Thermal management systems

ABSTRACT

A heat transfer apparatus includes a plurality of “n” number of control valves, each of the plurality of “n” number of control valves including a control valve inlet and a control valve outlet; a like plurality of “n” number of evaporator sections, each of the like plurality of “n” number of evaporator sections including an evaporator section inlet and an evaporator section outlet, each evaporator section inlet fluidly coupled to a corresponding one of the plurality of “n” number of control valve outlets, each evaporator section configured to extract heat from at least one heat load that is in thermal conductive or convective contact or proximate to the evaporator section; a refrigerant fluid inlet fluidly coupled to the like plurality of evaporator sections; and a refrigerant fluid outlet fluidly coupled to the like plurality of evaporator sections.

CLAIM OF PRIORITY

This application claims priority under 35 USC § 119(e) to U.S.Provisional Patent Application Ser. No. 63/214,328, filed on Jun. 24,2021, and entitled “THERMAL MANAGEMENT SYSTEMS,” and U.S. ProvisionalPatent Application Ser. No. 63/228,685, filed on Aug. 3, 2021, andentitled “THERMAL MANAGEMENT SYSTEMS.” The entire contents of bothprevious applications are hereby incorporated by reference.

BACKGROUND

Refrigeration systems absorb thermal energy from heat sources operatingat temperatures below the temperature of the surrounding environment anddischarge thermal energy into the surrounding environment. Heat sourcesoperating at temperatures above the surrounding environment can benaturally cooled by the surrounding if there is direct contact betweenthe source and the environment.

Conventional refrigeration systems include a compressor, a heatrejection exchanger (i.e., a condenser), a receiver, an expansiondevice, and a heat absorption exchanger (i.e., an evaporator). Suchsystems can be used to maintain operating temperature set points for awide variety of cooled heat sources (loads, processes, equipment,systems) thermally interacting with the evaporator. Closed-circuitrefrigeration systems may pump significant amounts of absorbed thermalenergy from heat sources into the surrounding environment.

In closed-circuit systems, compressors are used to compress vapor froman evaporating pressure the evaporator and to a condensing pressure inthe condensers and condense the compressed vapor converting the vaporinto a liquid at a temperature higher than the surrounding environmenttemperature. The combination of condensers and compressors can add asignificant amount of weight and can consume relatively large amounts ofelectrical power. In general, the larger amount of absorbed thermalenergy that the system is designed to handle, the heavier therefrigeration system and the larger amount of power consumed duringoperation, even when cooling of a heat source occurs over relativelyshort time periods.

In some cases the surrounding environment temperature can appear belowthe heat source temperature. The refrigeration system provides a contactvia refrigerant. There may be no need to compress vapor from theevaporating to condensing pressure since condensation can happen at apressure slightly higher or even below the evaporating pressure.

SUMMARY

This disclosure describes techniques related to systems and methods forthermal management. In an example implementation, a heat transferapparatus includes a plurality of “n” number of control valves, each ofthe plurality of “n” number of control valves including a control valveinlet and a control valve outlet; a like plurality of “n” number ofevaporator sections, each of the like plurality of “n” number ofevaporator sections including an evaporator section inlet and anevaporator section outlet, each evaporator section inlet fluidly coupledto a corresponding one of the plurality of “n” number of control valveoutlets, each evaporator section configured to extract heat from atleast one heat load that is in thermal conductive or convective contactor proximate to the evaporator section; a refrigerant fluid inletfluidly coupled to the like plurality of evaporator sections; and arefrigerant fluid outlet fluidly coupled to the like plurality ofevaporator sections.

In an aspect combinable with the example implementation, the pluralityof “n” number of control valves are fluidly coupled between therefrigerant fluid inlet and the evaporator outlets. In another aspectcombinable with any of the previous aspects, each of the plurality of“n” number of control valves is configured to receive a control signal.

In another aspect combinable with any of the previous aspects, therefrigerant fluid inlet includes an inlet distributor having a pluralityof outlets, with each of the plurality of outlets being coupled to theinlet of a corresponding one of the plurality of “n” number of controlvalves.

In another aspect combinable with any of the previous aspects, therefrigerant fluid outlet includes an outlet collector having a pluralityof inlets, with each of the plurality of inlets being coupled to theevaporator section outlet of a corresponding one of the like pluralityof evaporator sections.

In another aspect combinable with any of the previous aspects, theplurality of “n” number of control valves are configured to selectivelyexpand a refrigerant fluid to generate a refrigerant fluid mixtureincluding liquid refrigerant fluid and refrigerant fluid vapor; anddirect the refrigerant fluid mixture into the corresponding likeplurality of evaporator sections.

In another aspect combinable with any of the previous aspects, theplurality of “n” number of control valves include expansion valves thatare further configured to selectively stop a refrigerant fluid flowthrough the expansion valves.

In another example implementation, a method of cooling at least one heatload includes providing a flow of a refrigerant fluid to a refrigerantfluid inlet of a heat transfer device; providing the flow of therefrigerant fluid from the refrigerant fluid inlet to a plurality of “n”number of control valves, each of the plurality of “n” number of controlvalves including a control valve inlet and a control valve outlet;providing the flow of the refrigerant fluid from the refrigerant fluidinlet to a like plurality of “n” number of evaporator sections, each ofthe like plurality of “n” number of evaporator sections including anevaporator section inlet and an evaporator section outlet, eachevaporator section inlet fluidly coupled to a corresponding one of theplurality of “n” number of control valve outlets; extracting heat, withat least one evaporator section, from at least one heat load that is inthermal conductive or convective contact or proximate to the evaporatorsection; and providing the flow of the refrigerant fluid through arefrigerant fluid outlet fluidly coupled to the like plurality ofevaporator sections.

An aspect combinable with the example implementation further includesexpanding, in at least one of the a plurality of “n” number of controlvalves, the refrigerant fluid to generate a refrigerant fluid mixtureincluding liquid refrigerant fluid and refrigerant fluid vapor; anddirecting the refrigerant fluid mixture into the corresponding at leastone evaporator section.

Another aspect combinable with any of the previous aspects furtherincludes selectively stopping the flow of the refrigerant fluid throughthe heat transfer device with the control valves.

Another aspect combinable with any of the previous aspects furtherincludes directing the refrigerant fluid to enter a first set of “n”-“x”number of the plurality of evaporator sections over a first interval,while inhibiting the refrigerant fluid to enter a second, different setof “x” number of the plurality of evaporator sections over the firstinterval, where “n” is a total number of the plurality of evaporatorsections.

Another aspect combinable with any of the previous aspects furtherincludes switching the refrigerant fluid to direct the transportedrefrigerant fluid that enters the gated evaporator to contact a third,different set of “n”- “x”′ number of the plurality of evaporatorsections over a second, subsequent interval, while inhibiting therefrigerant fluid to enter a fourth, different set of “x”′ number of theplurality of evaporator sections over the second interval.

In another example implementation, a thermal management system includesan open-circuit refrigeration system (OCRS), an exhaust line, and a flowcontrol device. The OCRS includes a receiver configured to store arefrigerant fluid and at least one gated evaporator. The gatedevaporator is configured to extract heat from a plurality of heat loadswhen the plurality of heat loads are in thermal conductive or convectivecontact or proximate to the gated evaporator. The gated evaporatorincludes a plurality of “n” number of control valves. Each of theplurality of “n” number of control valves includes a control valve inletand a control valve outlet. The gated evaporator further includes a likeplurality of evaporator sections. Each of the like plurality ofevaporator sections includes an evaporator section inlet and anevaporator section outlet. Each evaporator section inlet is coupled to acorresponding one of the plurality of “n” number of control valveoutlets. The flow control device includes an inlet and an outlet, withthe outlet coupled to an exhaust line. The flow control device isconfigured to control a refrigerant fluid pressure upstream of the flowcontrol device. The receiver, the gated evaporator, the flow controldevice, and the exhaust line are fluidly coupled to form an open-circuitrefrigerant fluid flow path.

An aspect combinable with the example implementation further includes aninlet distributor coupled to the outlet of the receiver, and having aplurality of outlets, with each of the plurality of outlets beingcoupled to the inlet of a corresponding one of the plurality of “n”number of control valves.

Another aspect combinable with any of the previous aspects furtherincludes an outlet collector having a plurality of inlets with each ofthe plurality of inlets being coupled to the evaporator section outletof a corresponding one of the like plurality of evaporator sections, andhaving an outlet coupled to the inlet of the flow control device.

In another aspect combinable with any of the previous aspects, theplurality of “n” number of control valves are configured to selectivelyexpand the refrigerant fluid to generate a refrigerant fluid mixtureincluding liquid refrigerant fluid and refrigerant fluid vapor; anddirect the refrigerant fluid mixture into the corresponding likeplurality of evaporator sections. In another aspect combinable with anyof the previous aspects, the plurality of “n” number of control valvesare expansion valves that are further configured to selectively stoprefrigerant fluid flow through the expansion valves.

In another aspect combinable with any of the previous aspects, theplurality of “n” number of control valves are expansion valves that arenot configured to stop refrigerant fluid flow through the expansionvalves, with the system further including a plurality of solenoidcontrol valves coupled to the expansion valves, the plurality ofsolenoid valves configured to selectively stop the refrigerant fluidflow through the expansion valves.

In another aspect combinable with any of the previous aspects, theplurality of “n” number of control valves are configured to selectivelyperform a constant-enthalpy expansion of a liquid refrigerant fluid togenerate a refrigerant fluid mixture for the like plurality ofevaporator sections.

In another aspect combinable with any of the previous aspects, therefrigerant fluid includes ammonia.

In another aspect combinable with any of the previous aspects, theplurality of “n” number of control valves are further configured tocontrol temperatures of the plurality of heat loads.

In another aspect combinable with any of the previous aspects, the flowcontrol device includes a back-pressure regulator connected downstreamfrom the evaporator along the open-circuit refrigerant fluid flow path.

In another aspect combinable with any of the previous aspects, theback-pressure regulator is configurable to receive refrigerant fluidvapor generated in the gated evaporator and to regulate the pressure ofthe refrigerant fluid upstream from the back-pressure regulator alongthe refrigerant fluid flow path.

In another aspect combinable with any of the previous aspects, theback-pressure regulator is configurable to discharge the refrigerantvapor through the exhaust line, without returning the refrigerant vaporto the receiver.

In another aspect combinable with any of the previous aspects, therefrigerant fluid from the exhaust line is discharged so that thedischarged refrigerant fluid is not returned to the receiver.

Another aspect combinable with any of the previous aspects furtherincludes a control system configured to respond to signals from at leastone sensor to control operation of the plurality of “n” number ofcontrol valves.

In another aspect combinable with any of the previous aspects, thecontrol system is configured to process the signals from the at leastone sensor to switch “x” number of the plurality of “n” number ofcontrol valves to inhibit refrigerant flow through the “x” number of theplurality of “n” number of control valves during a period, with “x”having a value that is at least one less than “n”.”

In another aspect combinable with any of the previous aspects, thecontrol system is configured to process signals that are time periodsignals to indicate that “x” number of uncooled evaporator sections havereached a maximum time period for a heat load operation, with “x” havinga value that is at least one less than “n.”

In another aspect combinable with any of the previous aspects, thecontrol system is configured to process signals that are temperaturesignals to indicate that “x” number of the uncooled evaporator sectionshave reached the maximum heat load temperature rise during a heat loadoperation, with “x” having a value that is at least one less than “n.”

In another aspect combinable with any of the previous aspects, thecontrol system is configured to process signals that are temperaturesignals to indicate that “x” number of uncooled evaporator sections havereached a maximum evaporator section temperature rise during a heat loadoperation, with “x” having a value that is at least one less than “n.”

In another aspect combinable with any of the previous aspects, the flowcontrol device is a first flow control device, and the system furtherincludes a second flow control device coupled between the receiveroutlet and the inlet to the flow distributer, with the second flowcontrol device configured to control vapor quality at the outlet of thegated evaporator.

Another aspect combinable with any of the previous aspects furtherincludes a closed-circuit refrigeration system (CCRS) integrated withthe OCRS.

Another aspect combinable with any of the previous aspects furtherincludes a liquid separator having an inlet, a vapor-side outlet, and aliquid-side outlet.

In another aspect combinable with any of the previous aspects, the CCRSincludes a compressor having a compressor inlet fluidly coupled to thevapor-side outlet and having a compressor outlet; and a condenser havinga condenser inlet fluidly coupled to the compressor outlet and having acondenser outlet coupled to an inlet of the receiver to condense asuperheated refrigerant vapor at the condenser inlet by removing heatfrom the refrigerant fluid.

Another aspect combinable with any of the previous aspects furtherincludes a junction having an inlet fluidly coupled to the vapor-sideoutlet of the liquid separator and first and second outlets fluidlycoupled to the compressor inlet and the inlet of the flow controldevice.

Another aspect combinable with any of the previous aspects furtherincludes an electronically controllable expansion valve; a sensordisposed downstream of the gated evaporator to generate a sensor signalthat directly or indirectly controls the electronically controllableexpansion valve.

Another aspect combinable with any of the previous aspects furtherincludes a recuperative heat exchanger that has a first fluid path thatreceives the refrigerant fluid from the receiver and a second fluid paththat receives refrigerant vapor from the vapor-side outlet, with thesecond fluid path providing thermal contact between the refrigerantfluid leaving the receiver and the refrigerant vapor passing through therecuperative heat exchanger.

In another aspect combinable with any of the previous aspects, therecuperative heat exchanger evaporates any remaining liquid prior tobeing fed to the inlet of the compressor.

Another aspect combinable with any of the previous aspects furtherincludes an electronically controllable expansion valve; a sensordisposed downstream of the gated evaporator to generate a sensor signalthat directly or indirectly controls the electronically controllableexpansion valve, with the electronically controlled expansion valveoperated with the sensor to maintain a superheat at an outlet of therecuperative heat exchanger.

In another aspect combinable with any of the previous aspects, therecuperative heat exchanger is configured to transfer heat energy fromthe refrigerant fluid emerging from liquid separator to refrigerantfluid upstream from the electronically controllable expansion valve.Another aspect combinable with any of the previous aspects furtherincludes an ejector having a primary inlet, a secondary inlet, and anoutlet, with the primary inlet fluidly coupled to receive refrigerantfrom the receiver, and the secondary inlet fluidly coupled to receiverefrigerant fluid from the liquid-side outlet of the liquid separator.

In another aspect combinable with any of the previous aspects, theejector is configured to pump a secondary refrigerant fluid flowreceived at the secondary inlet from the liquid side outlet using energyof a primary refrigerant flow from the receiver outlet.

Another aspect combinable with any of the previous aspects furtherincludes a pump having an inlet and an outlet, with the inlet fluidlycoupled to the liquid-side outlet of the liquid separator and the outletfluidly coupled to an inlet of the gated evaporator.

In another aspect combinable with any of the previous aspects, the pumpis configured to circulate a refrigerant fluid flow received from theliquid-side outlet of the liquid separator to the inlet of the gatedevaporator.

Another aspect combinable with any of the previous aspects furtherincludes a control system configured to control operation of the gatedevaporator, the control system including a processor device, memory andstorage operatively connected.

In another aspect combinable with any of the previous aspects, thecontrol system is configured to produce a first control signal to directtransported refrigerant fluid to enter a first set of fewer than thelike plurality of evaporator sections over a first interval, andinhibits the refrigerant fluid to enter a second, different set of thefewer than the like plurality of evaporator sections over the firstinterval; and produce a second control signal to direct the transportedrefrigerant fluid that enters the gated evaporator to contact a third,different set of the evaporator sections over a second, subsequentinterval, and inhibits the refrigerant fluid to enter a fourth,different set of the fewer than the plural evaporator sections over thesecond interval.

In another example implementation, a thermal management method includestransporting a refrigerant fluid from a receiver, through a gatedevaporator having a plurality of evaporator sections configured toextract heat from a plurality of heat loads when the plurality of heatloads are in thermal conductive or convective contact or are inproximity to the gated evaporator, through a flow control device tocontrol to control refrigerant fluid pressure upstream of the flowcontrol device, and to an exhaust line of an open-circuit refrigerationsystem. The method further includes directing the transportedrefrigerant fluid to enter a first set of “n”- “x” number of theplurality of evaporator sections over a first interval, while inhibitingthe refrigerant fluid to enter a second, different set of “x” number ofthe plurality of evaporator sections over the first interval, where “n”is a total number of the plurality of evaporator sections. The methodfurther includes switching the refrigerant fluid to direct thetransported refrigerant fluid that enters the gated evaporator tocontact a third, different set of “n”- “x”′ number of the plurality ofevaporator sections over a second, subsequent interval, while inhibitingthe refrigerant fluid to enter a fourth, different set of “x”′ number ofthe plurality of evaporator sections over the second interval. Themethod further includes discharging refrigerant vapor that is generatedby the plurality of heat loads from the exhaust line so that thedischarged refrigerant vapor is not returned to the receiver.

In an aspect combinable with the example implementation, the flowcontrol device is a first flow control device, and the method furtherincludes controlling a vapor quality of the refrigerant fluid at anoutlet of the gated evaporator by operation of a second flow controldevice.

In another aspect combinable with any of the previous aspects, switchingoccurs by controlling operation of a plurality of control valves coupledto a plurality of outlets of an inlet distributor of the gatedevaporator, with the plurality of outlets being coupled to inlets of theplurality of evaporator sections.

Another aspect combinable with any of the previous aspects furtherincludes collecting refrigerant flows by an outlet collector having aplurality of inlets coupled to evaporator section outlets.

Another aspect combinable with any of the previous aspects furtherincludes expanding, by the plurality of control valves, the refrigerantfluid to generate a refrigerant fluid mixture including liquidrefrigerant and refrigerant vapor; and directing the refrigerant fluidmixture into the corresponding evaporator sections.

In another aspect combinable with any of the previous aspects, theplurality of control valves are expansion valves that are configured toselectively stop refrigerant fluid through the expansion valves.

In another aspect combinable with any of the previous aspects, theplurality of “n” number of control valves are expansion valves that arenot configured to stop refrigerant fluid through the expansion valves,and the method further includes operating a plurality of solenoidcontrol valves fluidly coupled to the expansion valves to selectivelystop the refrigerant fluid through the expansion valves.

In another aspect combinable with any of the previous aspects, theplurality of control valves are configured to selectively perform aconstant-enthalpy expansion of the liquid refrigerant fluid to generatethe refrigerant fluid mixture for the evaporator sections.

In another aspect combinable with any of the previous aspects, therefrigerant fluid includes ammonia.

In another aspect combinable with any of the previous aspects, theplurality of control valves are configured to control temperatures ofthe heat loads.

In another aspect combinable with any of the previous aspects,discharging includes discharging the refrigerant vapor through aback-pressure regulator.

In another aspect combinable with any of the previous aspects, theback-pressure regulator is configured to receive refrigerant vaporgenerated in the gated evaporator and to regulate the pressure of therefrigerant fluid upstream from the back-pressure regulator.

In another aspect combinable with any of the previous aspects, theback-pressure regulator is configured to discharge the refrigerant vaporthrough the exhaust line without returning the refrigerant vapor to thereceiver.

In another aspect combinable with any of the previous aspects, therefrigerant fluid from the exhaust line is discharged so that thedischarged refrigerant vapor is not returned to the receiver.

Another aspect combinable with any of the previous aspects furtherincludes operating a control system to respond to signals from sensorsto control operation of the plurality of control valves; and process thesignals from the sensor to switch “x” number of the plurality of controlvalves to inhibit refrigerant flow through the “x” number of theplurality of control valves during the first interval, with “x” having avalue that is at least one less than “n.”

Another aspect combinable with any of the previous aspects furtherincludes operating the control system to process the signals as timeperiod signals to indicate that “x” number of uncooled evaporatorsections have reached a maximum time period for proper heat loadoperation, with “x” having a value that is at least one less than “n”.

Another aspect combinable with any of the previous aspects furtherincludes operating the control system to process the signals astemperature signals to indicate that “x” number of the uncooledevaporator sections have reached the maximum heat load temperature riseduring the heat load operation, with “x” having a value that is at leastone less than “n.”

Another aspect combinable with any of the previous aspects furtherincludes operating the control system to process the signals astemperature signals to indicate that “x” number of uncooled evaporatorsections have reached a maximum evaporator section temperature riseduring the heat load operation, with “x” having a value that is at leastone less than “n.”

In another aspect combinable with any of the previous aspects, the flowcontrol device is a first flow control device, and the method furtherincludes controlling vapor quality at the outlet of the gated evaporatorwith a second flow control device fluidly coupled between the receiveroutlet and the inlet to the flow distributer.

In another aspect combinable with any of the previous aspects,transporting the refrigerant fluid includes transporting the refrigerantfluid through a closed-circuit refrigeration system that is integratedwith the open-circuit refrigeration system.

Another aspect combinable with any of the previous aspects furtherincludes transporting the refrigerant fluid through a liquid separatorhaving an inlet, a vapor-side outlet, and a liquid-side outlet.

Another aspect combinable with any of the previous aspects furtherincludes transporting the refrigerant fluid to a compressor of theclosed-circuit refrigeration system, the compressor having a compressorinlet coupled to the vapor-side outlet and having a compressor outlet;and transporting the refrigerant fluid to a condenser having a condenserinlet coupled to the compressor outlet and having a condenser outletcoupled to an inlet of the receiver to condense a superheated vapor atthe condenser inlet by removing heat from the refrigerant fluid.

Another aspect combinable with any of the previous aspects furtherincludes receiving refrigerant fluid from the receiver by a recuperativeheat exchanger that has a first fluid path that receives the refrigerantfluid from the receiver and a second fluid path that receivesrefrigerant vapor from the vapor-side outlet, with the second fluid pathproviding thermal contact between the refrigerant fluid leaving thereceiver and refrigerant vapor passing through the recuperative heatexchanger.

Another aspect combinable with any of the previous aspects furtherincludes evaporating any remaining refrigerant liquid in therecuperative heat exchanger prior to the inlet of the compressor.

Another aspect combinable with any of the previous aspects furtherincludes transporting refrigerant fluid from the liquid side outlet ofthe liquid separator to a secondary inlet of an ejector that further hasa primary inlet and an outlet, with the primary inlet fluidly coupled toreceive refrigerant from the receiver, and the outlet fluidly coupled todeliver refrigerant fluid to the inlet of the liquid separator.

Another aspect combinable with any of the previous aspects furtherincludes pumping, with the ejector, a secondary refrigerant fluid flowreceived by the secondary inlet from the liquid side outlet using energyof a primary refrigerant flow from the receiver outlet.

Another aspect combinable with any of the previous aspects furtherincludes pumping, with a pump, refrigerant liquid from the liquid-sideoutlet of the liquid separator to an inlet of the gated evaporator.

The above aspects or other aspects of the disclosed aspects may includeone or more of the following advantages.

The aspects enable cooling of large loads and high heat loads that arealso highly temperature sensitive with an undersized cooling system,i.e., a cooling system that has a cooling capacity that is less than theexpected cooling capacity for all of the heat loads, and yet which stillovercomes some of the problems associated with the conventionalclosed-cycle refrigeration systems. This undersized cooling system cancomprise an open-circuit refrigeration system or a closed-circuitrefrigeration system or an open-circuit refrigeration system integratedwith a closed-circuit refrigeration system.

The details of one or more embodiments are set forth in accompanyingdrawings and the description below. Other features and advantages willbe apparent from the description, drawings, and claims.

DESCRIPTION OF DRAWINGS

FIG. 1 is a schematic diagram of an example of a thermal managementsystem (TMS) that includes an open-circuit refrigeration system (OCRS)according to the present disclosure.

FIG. 2 is a schematic diagram of an example implementation of a gatedevaporator implemented in example embodiments of a TMS according to thepresent disclosure.

FIGS. 3A and 3B are flow diagrams of cooling initiation processes for agated evaporator according to the present disclosure.

FIGS. 4-6 are schematic diagrams of example implementations of a TMSthat includes at least one of an OCRS and a closed-circuit refrigerationsystem (CCRS) according to the present disclosure.

FIG. 7 is a block diagram of an example control system (or controller)for a TMS according to the present disclosure.

FIG. 8 is a schematic diagram of an example of a TMS that includes apower generation apparatus.

FIG. 9 is a schematic diagram of an example of directed energy systemthat includes a TMS.

DETAILED DESCRIPTION

Cooling of large loads and high heat loads that are also highlytemperature sensitive can present a number of challenges. On one hand,such loads generate significant quantities of heat that is extractedduring cooling. In conventional closed-cycle refrigeration systems,cooling high heat loads typically involves circulating refrigerant fluidat a relatively high mass flow rate. However, closed-cycle systemcomponents that are used for refrigerant fluid circulation—includinglarge compressors to compress vapor at a low pressure to vapor at a highpressure and condensers to remove heat from the compressed vapor at thehigh pressure and convert to a liquid— are heavy and consume significantpower. As a result, many closed-cycle systems are not well suited fordeployment in mobile platforms—such as on small vehicles or inspace—where size and weight constraints may make the use of largecompressors and condensers impractical.

On the other hand, temperature sensitive loads such as electroniccomponents and devices may require temperature regulation within arelatively narrow range of operating temperatures. Maintaining thetemperature of such a load to within a small tolerance of a temperatureset point can be challenging when a single-phase refrigerant fluid isused for heat extraction, since the refrigerant fluid itself willincrease in temperature as heat is absorbed from the load.

Directed energy systems that are mounted to mobile vehicles, such astrucks, or that exist in space may present many of the foregoingoperating challenges, as such systems may include high heat loads andtemperature sensitive components that require precise cooling duringoperation in a relatively short time. The thermal management systemsdisclosed herein, while generally applicable to the cooling of a widevariety of heat loads, are particularly well suited for operation withsuch directed energy systems.

In some cases, the TMS may be specified to cool two different kinds ofheat loads—high heat loads (e.g., highly temperature sensitivecomponents) operative for short periods of time and low heat loads(relative to the high heat loads) operative continuously or forrelatively long periods (relative to the high heat loads). However, tospecify a refrigeration system for the high heat load may result in arelatively large and heavy refrigeration system with a concomitant needfor a large and heavy power system to sustain operation of therefrigeration system.

For cooling of large heat loads and high heat loads that are also highlytemperature sensitive using conventional refrigeration systems wouldrequire use of closed-cycle system components such as relatively largeand heavy compressors to compress vapor at a low pressure to vapor at ahigh pressure and relatively large and heavy condensers to remove heatfrom the compressed vapor. In addition to being large and heavy, thesecomponents typically consume significant amounts of electrical power.

At the same time, the disclosed TMS may be undersized for the givenapplication. That is, the refrigerant flow rate is less than therequired refrigerant for a given amount of refrigeration over aspecified period of operation. Whereas conventional refrigerationsystems would be designed for the maximum flow rate needed forrefrigeration, the systems and methods disclosed herein use modifiedevaporator designed, coupled with refrigerant switching to providerefrigeration for heat loads to maintain temperature of those heat loadswith defined temperature ranges.

In some aspects, “refrigeration” as used in the present disclosure canmean a system (or multiple systems fluidly coupled) that operates togenerate a purposeful change of a characteristic of a coolant (e.g., arefrigerant fluid) to effectuate or increase heat transfer between twomediums (one of which can be the coolant). The purposeful change of thecharacteristic can be, for example, a change in pressure (e.g.,depressurization) of a pressurized coolant though an expansion valve. Insome embodiments, the change in pressure can include a phase change ofthe coolant, such as a liquid-to-gas phase change (e.g., endothermicvaporization). In some embodiments, pressurization of the refrigerantcan be performed by a powered (e.g., electrically or otherwise)component, such as (but not limited to) a compressor. In someembodiments, pressurization can be performed as part of therefrigeration cycle (e.g., a closed-cycle refrigeration process in whichgaseous refrigerant is substantially or completely recycled andcompressed into a liquid state) or prior to use (e.g., storingpre-compressed liquid refrigerant for later use in an open-cyclerefrigeration process in which a reserve of liquid refrigerant is usedbut substantially not recycled). In some embodiments, the phase changecan be driven by heating a liquid refrigerant with a very low boilingpoint (e.g., ammonia as used in an absorption-type refrigeration cycle).

Referring now to FIG. 1 , a thermal management system (TMS) 100 includesan open circuit refrigeration system (OCRS) 5 that utilizes one or morea gated (i.e., Gatling-type) evaporators 116 (herein referred to as an“evaporator 116” unless otherwise noted) to cool one or more heat loads118. The OCRS 5 includes a receiver 110 having a receiver inlet 109 andreceiver outlet 111 and storing a refrigerant fluid 1, an optionalsolenoid valve 112 having an inlet 113 and an outlet 115, a flow controldevice 114 (e.g., an expansion valve 114), the evaporator 116 having aninlet 121 and an outlet 123, and a solenoid valve 16 having an inlet 17and an outlet 19. The aforementioned components of OCRS 5 areinterconnected by one or more conduit sections to form an open circuitrefrigerant fluid path. An optional flow control device 12 having inlet13 and outlet 15 and optional check valve 14 are positioned along thegas flow path between the optional gas receiver 10 and the receiver 110.

As will be discussed below in FIG. 2 , the gated or “Gatling-type”evaporator 116 is an evaporator that has multiple evaporator sections,and the TMS 100 controls which evaporator sections, and hence, heatloads, receive refrigerant fluid 1 at a given interval of time. For aTMS 100 such as in FIG. 1 , the gated or Gatling type evaporator 116 canbe used for cooling high heat loads 118 when there are more high heatloads 118 available for powering than a total amount of available power.Generally, the OCRS 5 will deliver as much refrigerant fluid 1 as neededto cool the designed-for-total number of high heat loads 118 for the TMS100.

However, when the power requirements of the total number of high heatloads 118, ‘g,’ is higher than available power, the TMS 100 isconfigured to cool ‘g—k’ powered heat loads 118, where ‘g’ is the totalnumber of high heat loads 118 and ‘k’ is a number of high heat loads 118that are off, i.e., not powered nor outputting heat. Thus, one or moreof the high heat loads 118 thermally coupled to evaporator 116 areunpowered high heat loads and remaining ones of the heat loads 118 arepowered high heat loads.

The evaporator 116 is referred to as a Gatling evaporator because itsprincipal of operation is somewhat analogous or reminiscent of a Gatlinggun. The Gatling gun's operation centered on a cyclic multi-barreldesign which facilitated cooling and synchronized the firing-reloadingsequence. As the hand wheel is cranked, the barrels rotate clockwise andeach barrel sequentially loads a single cartridge from a top-mountedmagazine, fires off the shot when it reaches a set position (usually at4 o'clock), then ejects the spent casing out of the left side at thebottom, after which the barrel is empty and allowed to cool untilrotated back to the top position and gravity-fed another new round. Thisconfiguration eliminated the need for a single reciprocating bolt designand allowed higher rates of fire to be achieved without the barrelsoverheating quickly.

The gated or Gatling type evaporator 116 operates in a somewhatanalogous or similar manner, by distributing the inlet refrigerantstream over fewer than the total number of evaporator sections thatcomprise the gated evaporator 116 as discussed in FIG. 2 . Evaporator116 can be implemented in a variety of ways. In general, evaporator 116functions as a heat exchanger, providing thermal conductive and/orconvective contact between the refrigerant fluid 1 and the high heatloads 118 (and/or other heat loads as described herein). Typically,evaporator 116 allows streams of refrigerant fluid 1 to flow through theevaporator 116 and absorb heat from the heat loads 118.

In this example, one or more heat loads 118 can be considered high heatloads that are in thermal conductive and/or convective contact or inproximity with the evaporator section 116. OCRS 5 optionally includesgas receiver 10 with the outlet 11 fluidly coupled to the inlet 109 ofthe receiver 110 via conduit, such that a gas flow path extends betweenthe gas receiver 10 and the receiver 110 (that stores the refrigerantfluid 1). The optional flow control device 12 having inlet 13 and outlet15, as well as the optional check valve 14 are positioned along the gasflow path between the optional gas receiver 10 and the receiver 110.

Receiver 110 is typically implemented as an insulated vessel that storesa refrigerant fluid at relatively high pressure. When ambienttemperature is very low and, as a result, pressure in the receiver 110is low and insufficient to drive refrigerant fluid flow through the TMS100, gas from gas receiver 10 can be directed into receiver 110. The gascompresses liquid refrigerant fluid 1 in receiver 110, maintaining theliquid refrigerant fluid 1 in a sub-cooled state, even when ambienttemperature and the temperature of the liquid refrigerant fluid arerelatively high. Receiver 110 can also include insulation applied aroundthe receiver 110 and a heater to reduce thermal losses.

In some aspects, receiver 110 includes the inlet 109 and the outlet 111,and may include an optional pressure relief valve. To charge receiver110, refrigerant fluid is typically introduced into receiver 110 via theinlet 109, and this can be done, for example, at service locations.Operating in the field the refrigerant exits receiver 110 through outlet111 that is connected to conduit. In case of emergency, if the fluidpressure within receiver 110 exceeds a pressure limit value, a pressurerelief valve opens to allow a portion of the refrigerant fluid to escapethrough valve to reduce the fluid pressure within receiver 110. Receiver110 is typically implemented as an insulated vessel that stores arefrigerant fluid at relatively high pressure. Receiver 110 can alsoinclude insulation applied around the receiver to reduce thermal losses.

In general, receiver 110 can have a variety of different shapes. In someembodiments, for example, the receiver is cylindrical. Examples of otherpossible shapes include, but are not limited to, rectangular prismatic,cubic, and conical. In certain embodiments, receiver 110 can be orientedsuch that outlet 111 is positioned at the bottom of the receiver 110. Inthis manner, the liquid portion of the refrigerant fluid 1 withinreceiver 110 is discharged first through outlet 111, prior to dischargeof refrigerant vapor. In certain embodiments, the refrigerant fluid 1can be an ammonia-based mixture that includes ammonia and one or moreother substances. For example, mixtures can include one or moreadditives that facilitate ammonia absorption or ammonia burning.

During operation of OCRS 5, cooling can be initiated by a variety ofdifferent mechanisms. In some embodiments, for example, OCRS 5 includesa temperature sensor attached to heat load 22 (as will be discussedsubsequently) or to certain of heat loads 118. When the temperature ofheat load 22 exceeds a certain temperature set point (i.e., thresholdvalue), a control system 999 (described in additional detail below)connected to the temperature sensor can initiate cooling of heat load22. Alternatively, in certain embodiments, OCRS 5 operates essentiallycontinuously—provided that the pressure within receiver 110 issufficient—to cool heat loads 118. As soon as receiver 110 is chargedwith refrigerant fluid, refrigerant fluid is ready to be directed intoevaporator 116 to cool heat loads 118. In general, cooling is initiatedwhen a user of the system or the heat load issues a cooling demand.

The TMS 100, as all disclosed embodiments, may also include a controlsystem (or controller) 999 (see FIG. 7 for an exemplary embodiment) thatproduces control signals (based on sensed thermodynamic properties) tocontrol operation of one or more of the various devices, e.g., optionalsolenoid control valve 112, expansion valve 114, etc., as needed, aswell as to control operation of a motor of a compressor 104, a fan 108,or other components in other example implementations of a TMS. Controlsystem 999 may receive signals, process received signals and sendsignals (as appropriate) from/to the sensors and control devices tooperate the TMS 100.

The term “control system,” as used herein, can refer to an overallsystem that provides control signals and receives feedback data fromunit controllers, such as unit controllers (e.g., programmable logiccontrollers, motor controllers, variable frequency drives, actuators).In some aspects, the control system includes the overall system and theunit controllers. In some aspects, a control system simply refers to asa single unit controller or a network of two or more individual unitcontrollers that communicate directly with each other (rather than withan overall system.

The process streams (e.g., refrigerant flows, ambient airflows, otherheat exchange fluid flows) in a TMS according to the present disclosure,as well as process streams within any downstream processes with whichthe TMS is fluidly coupled, can be flowed using one or more flow controlsystems (e.g., that include the control system 999) implementedthroughout the system. A flow control system can include one or moreflow pumps, fans, blowers, or solids conveyors to move the processstreams, one or more flow pipes through which the process streams areflowed and one or more valves to regulate the flow of streams throughthe pipes, whether shown in the exemplary figures or not. Each of theconfigurations described herein can include at least one variablefrequency drive (VFD) coupled to a respective pump or fan that iscapable of controlling at least one fluid flow rate. In someimplementations, liquid flow rates are controlled by at least one flowcontrol valve.

In some embodiments, a flow control system can be operated manually. Forexample, an operator can set a flow rate for each pump or transferdevice and set valve open or close positions to regulate the flow of theprocess streams through the pipes in the flow control system. Once theoperator has set the flow rates and the valve open or close positionsfor all flow control systems distributed across the system, the flowcontrol system can flow the streams under constant flow conditions, forexample, constant volumetric rate or other flow conditions. To changethe flow conditions, the operator can manually operate the flow controlsystem, for example, by changing the pump flow rate or the valve open orclose position.

In some embodiments, a flow control system can be operatedautomatically. For example, the flow control system can be connected toa computer or control system (e.g., control system 999) to operate theflow control system. The control system can include a computer-readablemedium storing instructions (such as flow control instructions and otherinstructions) executable by one or more processors to perform operations(such as flow control operations). An operator can set the flow ratesand the valve open or close positions for all flow control systemsdistributed across the facility using the control system. In suchembodiments, the operator can manually change the flow conditions byproviding inputs through the control system. Also, in such embodiments,the control system can automatically (that is, without manualintervention) control one or more of the flow control systems, forexample, using feedback systems connected to the control system. Forexample, a sensor (such as a pressure sensor, temperature sensor orother sensor) can be connected to a pipe through which a fluid flows.The sensor can monitor and provide a flow condition (such as a pressure,temperature, or other flow condition) of the process stream to thecontrol system. In response to the flow condition exceeding a threshold(such as a threshold pressure value, a threshold temperature value, orother threshold value), the control system can automatically performoperations. For example, if the pressure or temperature in the pipeexceeds the threshold pressure value or the threshold temperature value,respectively, the control system can provide a signal to the pump todecrease a flow rate, a signal to open a valve to relieve the pressure,a signal to shut down process stream flow, or other signals.

Upon initiation of a cooling operation, refrigerant fluid 1 fromreceiver 110 is discharged from the receiver outlet 111 and throughoptional solenoid valve 112 if present. As discussed above, the drivingforce for the transport of refrigerant fluid 1 through OCRS 5 is thepressure within receiver 110. Refrigerant fluid is transported throughconduit to expansion valve 114, which directly or indirectly controlsvapor quality (see discussion below) at the evaporator outlet 123. Itshould be understood that more generally, expansion valve 114 can beimplemented as any component or device that performs the functionalsteps described below and provides for vapor quality control at theevaporator outlet 123.

Once inside the expansion valve 114, the refrigerant fluid 1 undergoesconstant enthalpy expansion from an initial pressure p_(r) (i.e., thereceiver pressure) to an evaporation pressure pc at the outlet 119 ofthe expansion valve 114. In general, the evaporation pressure pc dependson a variety of factors, most notably the desired temperature set pointvalue (i.e., the target temperature) at which each of the heat loads 118are to be maintained and the heat input generated by the heat loads 118.

The initial pressure in the receiver 110 tends to be in equilibrium withthe surrounding temperature and is different for different refrigerantfluids. The pressure in the evaporator 116 depends on the evaporatingtemperature, which is lower than the heat load temperature and isdefined during design of the system. The TMS 100 is operational as longthe receiver-to-evaporator pressure difference is sufficient to driveadequate refrigerant fluid flow through the expansion valve 114.

After undergoing constant enthalpy expansion in the expansion valve 114,the liquid refrigerant fluid is converted to a mixture of liquid andvapor phases at the temperature of the fluid and evaporation pressurepc. This two-phase refrigerant fluid mixture is transported toevaporator 116.

When the two-phase mixture of refrigerant fluid is directed intoevaporator 116, the liquid phase absorbs heat from heat loads 118,driving a phase transition of the liquid refrigerant fluid into thevapor phase. Because this phase transition occurs at (nominally)constant temperature, the temperature of the refrigerant fluid mixturewithin evaporator 116 remains unchanged, provided at least some liquidrefrigerant fluid remains in evaporator 116 to absorb heat.

Further, the constant temperature of the refrigerant fluid mixturewithin evaporator 116 can be controlled by adjusting the pressure pc ofthe refrigerant fluid, since adjustment of p_(e) changes the boilingtemperature of the refrigerant fluid. Thus, by regulating therefrigerant fluid pressure pc upstream from evaporator 116 (e.g., usingflow control device 16), the temperature of the two-phase refrigerantfluid mixture within evaporator 116 (and, nominally, the temperature ofheat loads 118) can be controlled to match a specific temperatureset-point value for each of the heat loads 118, ensuring that each ofthe heat loads 118 is maintained at, or very near, its targetedtemperature.

The pressure drop across the evaporator 116 causes drop of thetemperature of the refrigerant mixture (which is the evaporatingtemperature), but still the evaporator 116 can be configured to maintainthe heat loads temperatures within in set tolerances.

In some embodiments, for example, the evaporation pressure of therefrigerant fluid can be adjusted by flow control device 16 to ensurethat the temperature of heat loads 118 is maintained to within ±5degrees C. (e.g., to within ±4 degrees C., to within ±3 degrees C., towithin ±2 degrees C., to within ±1 degree C.) of the temperature setpoint value for heat loads 118.

As discussed above, within evaporator 116, a portion of the liquidrefrigerant in the two-phase refrigerant fluid mixture is converted torefrigerant vapor by undergoing a phase change. As a result, therefrigerant fluid mixture that emerges from evaporator 116 has a highervapor quality (i.e., the fraction of the vapor phase that exists inrefrigerant fluid mixture) than the refrigerant fluid mixture thatenters evaporator 116.

As the refrigerant fluid mixture emerges from evaporator 116, a portionof the refrigerant fluid can optionally be used to cool one or moreadditional thermal loads (not shown). Typically, for example, therefrigerant fluid that emerges from evaporator 116 is nearly in thevapor phase. The refrigerant fluid vapor (or, more precisely, high vaporquality fluid vapor) can be directed into a heat exchanger (not shown)coupled to another heat load, and can absorb heat from additional heatloads during propagation through the heat exchanger.

The two-phase refrigerant fluid mixture emerging from evaporator 116 istransported through conduit to flow control device 16, which directly orindirectly controls the upstream pressure, that is, the evaporatingpressure pc in the system. After passing through flow control device 16,the vapor component of the two-phase refrigerant fluid mixture isdischarged as exhaust through an exhaust line 20 of OCRS 5. Refrigerantvapor discharge can occur directly into the environment surrounding OCRS5. Alternatively, in some embodiments, the refrigerant vapor can befurther processed; various features and aspects of such processing arediscussed below.

It should be noted that the foregoing steps, while discussedsequentially for purposes of clarity, occur simultaneously andcontinuously during cooling operations. In other words, refrigerantvapor is continuously being discharged from receiver 110, refrigerantfluid mixture undergoes continuous expansion in expansion valve 114,flowing continuously through evaporator 116 and flow control device 16,and being discharged from OCRS 5, while heat loads 118 are being cooled.

As discussed above, during operation of OCRS 5, as refrigerant fluid 1is drawn from receiver 110 and used to cool heat loads 118, the pressuredriving the refrigerant fluid in receiver 110 through the system can bemaintained at a constant value for an extended period of operation byintroducing gas from optional gas receiver 10 into receiver 110. Insystems where a common receiver is charged with both refrigerant fluid 1and gas (as described above) or when optional gas receiver 10 isundercharged initially with gas, the period during which constantpressure can be maintained in receiver 110 may be compromised.

If the pressure within receiver 110 falls sufficiently, the capacity ofOCRS 5 to maintain a particular temperature set point value for heatloads 118 may be compromised. Therefore, the pressure in the receiver110, in the optional gas receiver 10, or the pressure drop across theexpansion valve 114 (or any related refrigerant fluid pressure orpressure drop in OCRS 5) can be measured and used to adjust operation ofthe expansion valve 114.

In addition, one or more measured pressure values can provide anindicator of the remaining operational time. An appropriate warningsignal can be issued (e.g., by a control system 999) to indicate that incertain period of time, the system may no longer be able to maintainadequate cooling performance; operation of the system can even be haltedif the pressure in receiver 110 (or any other measured pressure value inOCRS 5) reaches a low-end threshold value.

It should be noted that while in FIG. 1 only a single receiver 110 isshown, in some embodiments, OCRS 5 can include multiple receivers toallow for operation of the system over an extended time period. Each ofthe multiple receivers 110 can supply refrigerant fluid 1 to the systemto extend to total operating time period. Some embodiments may includeplurality of evaporators connected in parallel, which may or may notaccompanied by plurality of expansion valves 114 and plurality ofevaporators 116.

The expansion valve 114 functions as a flow control device. In general,expansion valve 114 can be implemented as any one or more of a varietyof different mechanical and/or electronic devices. For example, in someembodiments, expansion valve 114 can be implemented as a fixed orifice,a capillary tube, and/or a mechanical or electronic expansion valve. Ingeneral, fixed orifices and capillary tubes are passive flow restrictionelements which do not actively regulate refrigerant fluid flow.Mechanical expansion valves (usually called thermostatic or thermalexpansion valves) are typically flow control devices that enthalpicallyexpand a refrigerant fluid from a first pressure to an evaporatingpressure, controlling the superheat at the evaporator exit. Mechanicalexpansion valves generally include an orifice, a moving seat thatchanges the cross-sectional area of the orifice and the refrigerantfluid volume and mass flow rates, a diaphragm moving the seat, and abulb at the evaporator exit. The bulb is charged with a fluid and ithermetically fluidly communicates with a chamber above the diaphragm.The bulb senses the refrigerant fluid temperature at the evaporator exit(or another location) and the pressure of the fluid inside the bulb,transfers the pressure in the bulb through the chamber to the diaphragm,and moves the diaphragm and the seat to close or to open the orifice.

Typical electrical expansion valves include an orifice, a moving seat, amotor or actuator that changes the position of the seat with respect tothe orifice, a controller, and pressure and temperature sensors at theevaporator exit. The controller calculates the superheat for theexpanded refrigerant fluid based on pressure and temperaturemeasurements at the evaporator exit. If the superheat is above aset-point value, the seat moves to increase the cross-sectional area andthe refrigerant fluid volume and mass flow rates to match the superheatset-point value. If the superheat is below the set-point value the seatmoves to decrease the cross-sectional area and the refrigerant fluidflow rates.

Examples of suitable commercially available expansion valves that canfunction as expansion valve 114 include, but are not limited to,thermostatic expansion valves available from the Sporlan Division ofParker Hannifin Corporation (Washington, Mo.) and from Danfoss(Syddanmark, Denmark).

The flow control device 16 generally functions to control the fluidpressure upstream of the flow control device 16. In OCRS 5, flow controldevice 16 controls the refrigerant fluid pressure upstream from theevaporator 116 and flow control device 16. In general, flow controldevice 16 can be implemented as a back-pressure regulator (i.e.,back-pressure regulator 16) using a variety of different mechanical andelectronic devices. Typically, for example, back-pressure regulator 16is a device that regulates fluid pressure upstream from the regulator.In general, a wide range of different mechanical andelectrical/electronic devices can be used as back-pressure regulator.Typically, mechanical back-pressure regulating devices have an orificeand a spring supporting the moving seat against the pressure of therefrigerant fluid stream. The moving seat adjusts the cross-sectionalarea of the orifice and the refrigerant fluid volume and mass flowrates.

Typical electrical back-pressure regulating devices include an orifice,a moving seat, a motor or actuator that changes the position of the seatin respect to the orifice, a controller, and a pressure sensor at theevaporator exit or at the valve inlet. If the refrigerant fluid pressureis above a set-point value, the seat moves to increase thecross-sectional area of the orifice and the refrigerant fluid volume andmass flow rates to re-establish the set-point pressure value. If therefrigerant fluid pressure is below the set-point value, the seat movesto decrease the cross-sectional area and the refrigerant fluid flowrates.

In general, back-pressure regulators are selected based on therefrigerant fluid volume flow rate, the pressure differential across theregulator, and the pressure and temperature at the regulator inlet.Examples of suitable commercially available back-pressure regulatorsthat can function as back-pressure regulator include, but are notlimited to, valves available from the Sporlan Division of ParkerHannifin Corporation (Washington, Mo.) and from Danfoss (Syddanmark,Denmark).

Flow control device 12 is optional and is positioned between optionalgas receiver 10 and receiver 110. Without the control device 12, duringoperation of OCRS 5, gas in optional gas receiver 10 is discharged fromoptional gas receiver 10 directly into receiver 110 via conduit. Withflow control device 12 present in OCRS 5, flow control device 12functions to regulate the pressure within receiver 110, downstream fromthe flow control device 12. During operation of OCRS 5, flow controldevice 12 effectively maintains the total pressure within receiver 110at or above a target pressure value adequate to provide for sub-coolingof refrigerant fluid 1 in receiver 110, which maintains a particularrefrigerant mass flow rate through expansion valve 114 and evaporator116, and as a result, achieves a desired cooling capacity for one ormore thermal loads connected to OCRS 5. If the pressure within receiver110 falls below the target pressure value, flow control device 12 opensto allow additional gas from optional gas receiver 10 to enter receiver110, thereby increasing the pressure within receiver 110.

Flow control device 12 effectively functions as a flow regulation devicefor the gas in optional gas receiver 10, and is implemented as any oneor more of a variety of different mechanical and/or electronic devices.One example of such a device is a downstream pressure regulator (DPR),which is a device that regulates fluid pressure downstream from theregulator. Examples of suitable commercially available downstreampressure regulators that can function as flow control device 12 include,but are not limited to, regulators available from Emerson Electric (St.Louis, Mo.).

A variety of different gases can be introduced into optional gasreceiver 31 to control the gas pressure in receiver 110. In general,gases that are used are inert (or relatively inert) with respect to therefrigerant fluid. As an example, when a refrigerant fluid such asammonia is used, suitable gases that can be introduced into optional gasreceiver 10 include, but are not limited to, one or more of nitrogen,argon, xenon, and helium.

Turning now to FIG. 2 , and example implementation of evaporator 116 asa gated or Gatling evaporator 116 is shown. In some aspects, lightweight and compactness are generally requirements for a TMS to coolelectronic components that are, e.g. mobile or space based. In somecases, evaporator sections and/or heat loads are inherently heavy andcan carry substantial amount of thermal inertia. The evaporator 116discussed herein uses this built-in thermal inertia to increase TMScooling effectiveness and maintain the temperature tolerances in therange when undersized cooling systems are used.

In this example, gated evaporator 116 includes an inlet distributor 206that takes an inlet stream of refrigerant fluid 1, e.g., from thereceiver 110 or expansion valve 114 and distributes the inlet streamover a plurality (i.e., “n”) of control valves 204 a through 204 n (eachhaving an inlet 201 and an outlet 203) that feed a plurality ofevaporator sections 202 a through 202 n (each having an inlet 205 and anoutlet 207). Although shown as positioned upstream of evaporatorsections 202 a-202 n, control valves 204 a-204 n can be positioneddownstream (e.g., at outlets 207) of the corresponding evaporatorsections 202 a-202 n. Gated evaporator 116 also includes an outletcollector 208 that collects the “n” refrigerant streams and combines thecollected streams into a single outlet stream of refrigerant fluid 1.The evaporator 116 is configured into the plurality of evaporatorsections 202 a-202 n at least some of which are loaded with individualsets of high heat loads 118 and/or low heat loads 120. Each evaporatorsection 202 a-202 n includes a corresponding one of control valves 204a-204 b. Some of the evaporators sections 202 a-202 n includecorresponding one or ones of high heat loads 118 and corresponding oneor ones of low heat loads 120 attached to the corresponding evaporatorsection.

The control valves 204 a-204 n can be any valve that can be closed andopened. The control valves 204 a-204 n have inlets 201 coupled tooutlets of the inlet distributor 81 a. Examples of such control valves204 a-204 n include expansion valves or any other valve that allows orinhibits refrigerant flow into refrigerant channels of the evaporatorsections 202 a-202 n. The control valves 204 a-204 n are installedupstream of the evaporator sections 202 a-202 n in this example, withoutlets 203 fluidly coupled to inlets 205 of the evaporator sections 202a-202 n.

Each evaporator section 202 a-202 n further has outlets 207 coupled toinlets of the outlet distributor 208 that receives the “n” outletrefrigerant streams and collects the “n” outlet streams into onecomposite outlet stream that is fed to an inlet of the back-pressureregulator 16 (for example). In FIG. 2 , during operation, the collector208 can collect “x” less of the number of input steams “n” where “x” isin a range that is at least one and is less than or equal to two lessthan “n.”

The total cooling capacity of an undersized TMS is lower than the totalload applied by all high heat loads 118 and low heat loads 120. If anundersized TMS, as defined herein, would conventionally cool the highheat loads 118 and the low heat loads 120, the heat load demand wouldexceed the undersized TMS cooling capacity. As a result, an excessiveamount of vapor would be formed in refrigerant channels of an evaporatorsection. Over time of operation, the vapor in the refrigerant channelsof the evaporator section would increase, and the heat transfer rates inthe enlarged vapor region would abruptly degrade, and as a consequence,the heat transfer area interaction with the two-phase refrigerant wouldbe reduced. The vapor in the channels will produce excessive refrigerantpressure drops, thus degrading the overall cooling capacity of theundersized TMS. If the evaporators 116 are configured to operate in thetwo-phase region below the critical vapor quality, the negative impactwill be even greater.

To obviate above problem, the described undersized TMS 100 (and otherTMS as described herein) is configured to maintain temperatures of allheat loads within a temperature range. Prior to the engagement with thehigh heat loads 118 and low heat loads 120, all evaporator sections 202a-202 n and all heat loads 118 and 120 are precooled to the low-end ofthe temperature range. The described, undersized TMS 100 is configuredto adequately cool a reduced number (n-x) of the high heat loads 118 andlow heat loads 120 and related evaporator sections 202 a-202 n. Thereduced number is equal to the total number of heat loads/evaporatorsections “n” minus “x” heat loads.

During engagement, the power input is applied to all high heat loads 118and low heat loads 120 despite “x” number of evaporator sections 202a-202 n not receiving refrigerant. The loads/evaporator sections that donot receive refrigerant will be heated up as much as the thermal inertiapermits within the uncooled operational period. Then, at a certainmoment, e.g., upon receipt of a control signal 212, the control valves204 a-204 n redirect refrigerant flow to a different set of the reducednumber of the evaporator sections 202 a-202 n. Again, the uncooledloads/evaporator sections will be heated up as much as the thermalinertia allows to do that within the uncooled operational period. Thisprocess continues during operation of the heat loads, and isperiodically undated such that the temperature of the heat loads remainswithin allowed temperature range.

The purpose of redirecting refrigerant streams or switching sets ofcooled/uncooled evaporator sections, is to maximize the time ofoperation of the heat loads. The switching philosophy is based on usingat least one criterion that signals switching of the heat loads.Examples of criteria include determining that an uncooled evaporatorsection has reached a maximum time period for proper heat loadoperation. Another criterion is that the uncooled evaporator section hasreached the maximum heat load temperature rise during the heat loadoperation. Another criterion is that the uncooled evaporator section hasreaches the maximum evaporator section temperature rise during the heatload operation. Thus, the evaporator 116 can include a timer (not shown,but which can be provide by the control system 999) to measure thecriterion of evaporator sections 202 a-202 n having reached a maximumtime period for proper heat load operation or temperature sensors 210that measure the criterion that the uncooled evaporator section hasreached the maximum heat load temperature rise or the criterion that theuncooled evaporator section has reaches the maximum evaporator sectiontemperature rise. Other criteria including combinations of abovecriteria are possible.

Evaporator sections 202 a-202 n can be implemented in a variety of ways.In general, an evaporator section functions as a heat exchanger,providing thermal contact between the refrigerant fluid 1 and high heatload(s) 118 and/or low high heat load(s) 120. Typically, an evaporatorsection includes one or more fluid transport channels extendinginternally between an inlet and an outlet of the evaporator section,allowing refrigerant fluid to flow through the evaporator section andabsorb heat from heat load(s). A variety of different gated evaporatorscan be used in a TMS according to the present disclosure. In general, anevaporator section of the open-circuit refrigeration systems and theintegrated open and closed refrigeration systems disclosed herein canaccommodate any number of refrigerant fluid channels (includingmini/micro-channel tubes), blocks of printed circuit heat exchangingstructures, or more generally, any heat exchanging structures that areused to transport single-phase or two-phase fluids. The evaporator 116and/or components thereof, such as fluid transport channels, can beattached to the heat loads mechanically, or can be welded, brazed, orbonded to the heat load in any manner. An evaporator section can befabricated as part of a heat load(s) or otherwise integrated into one ormore of the heat loads (e.g., with integrated refrigerant fluidchannels). The portion of heat loads and refrigerant fluid channel(s)effectively functions as an evaporator section for an evaporator 116.

Referring now to FIG. 3A, a flow diagram that depicts a process 300 ofcooling high heat loads 118 is shown based on available power is shown.In some process 300 can be used, e.g., by or with the TMS 400 shown inFIG. 4 . The process 300 causes (step 302) a precool cycle in which eachof the evaporator sections 202 a-202 n is precooled to a temperaturevalue at the low end of the temperature range for the most temperaturesensitive of the high heat loads 118. The process 300 applies (step 304)power to selected ones of the high heat loads 118 according to high heatload control signals “g” in proximity of the precooled evaporatorsections 202 a-202 n, causing the powered high heat loads 118 to operateunder normal circumstances.

However, the process 300 directs (step 306) refrigerant fluid 1 to aselected number (g-k) of the evaporator sections 202 a-202 n, by openingrefrigerant flow to corresponding ones (g-k) of the control valves 204a-204 n, while closing others (k) of the control valves 204 a-204 n andthus inhibiting refrigerant flow to those corresponding evaporatorsections. That is, at least one less than the total number of controlvalves 204 a-204 n is inhibited from passing refrigerant flow into atleast one less of the corresponding evaporator sections 202 a-202 n. Theprocess 300 monitors each of the evaporator sections 204 a-204 naccording to one or more of above criteria. When the criteria is met(step 308), the process 300 repeats by sending control signals 212 tocontrol operation of a different set of the g—k powered high heat loads118 (step 310).

Referring now to FIG. 3B, a flow diagram that depicts a process 350 ofcooling heat loads 118 (e.g., in TMS 100) or high heat loads 118 and lowheat loads 120 (e.g., in TMS 200) is shown. The process 350 causes (step352) a precool cycle in which each of the evaporator sections 202 a-202n is precooled to a temperature value at the low end of the temperaturerange for the most temperature sensitive of the high heat loads 118 andthe low heat loads 120. The process 350 applies power (step 354 to sendhigh heat load control signals and step 356 to apply power) to all ofthe high heat loads 118 and the low heat loads 120 in proximity of theprecooled evaporator sections 202 a-202 n, causing the high heat loads118 and the low heat loads 120 to operate under normal circumstances.

However, the process 350 directs refrigerant (step 358) to a selectednumber (n-x) of the evaporator sections 202 a-202 n, by openingrefrigerant flow to corresponding ones (n-x) of the control valves 204a-204 n, while closing “x” others of the control valves 204 a-204 n andthus inhibiting refrigerant flow to those corresponding evaporatorsections. That is, at least one less than the total number of controlvalves 204 a-204 n is inhibited from passing refrigerant flow into atleast one less of the corresponding evaporator sections 202 a-202 n. Theprocess 350 monitors (step 360) each of the evaporator sections 202a-202 n according to one or more of above criteria.

As an example, process 350 inhibits refrigerant fluid to an evaporatorsection that has a high heat load and a low heat load. As the heat loadsoperate, the heat loads will each begin to rise in temperature. However,due to the thermal inertia of the evaporator section, that heat risewill be somewhat delayed and inhibited. For heat loads and an evaporatorsection that is not receiving refrigerant, the process 350 determines(step 360) when at least one of above criteria has been met for thatevaporator section 84 a.

When the criterion has been met for the evaporator section, the process350 will send (step 362) control signals to a different set of heatload(s) and direct (step 364) refrigerant to a different set of the n-xevaporator sections 202 a-202 n by causing the control valve and othersof the control valves 204 a-204 n to open, while simultaneously causingone of the remaining control valves 204 a-204 n to close, by shutting“OFF” the corresponding control valve 204 a-204 n, and causing theprocess 350 to repeat (step 364 to step 360) for a different set of oneor more control valves 204 a-204 n and heat loads. The repetition willensure that each evaporator section is uncooled for no more than “i”sequential cycles, where i is typically one or two, but could be more.

Consider that a particular control valve is next to be shut “OFF” thiswill result in refrigerant being inhibited from flowing through thatassociated evaporator section. As a result, the heat loads for thatassociated evaporator section will begin to rise in temperature.However, due to the thermal inertia of that evaporator section, the heatrise will be somewhat delayed and inhibited. The process 350 continuesto monitor each of the evaporator sections 202 a-202 n and for thatevaporator section, the heat rise will be somewhat delayed andinhibited. For heat loads and that evaporator section that now is notreceiving refrigerant, the process 350 determines whether at least oneof above criteria (step 360) has been met for that evaporator section.

When the criterion has been met for that evaporator section, the process350 will cause the control valve to open, while simultaneously causingone of the remaining control valves to close, by shutting “OFF” thecorresponding, remaining control valve. This process 350 will continueuntil such time as needed. Any switching paradigm can be used, and willvary according to the nature of the heat loads 118 and 120. In addition,time periods and/or temperature ranges can be different for differentones of the heat loads 118 and 120.

Further still, while in the example above, the process 350 inhibitedonly one evaporator section from receiving refrigerant at a time, inother embodiments more than one evaporator section can be inhibited fromreceiving refrigerant at a time, depending on specific designrequirements. Generally, when more than one evaporator section is shutoff from receiving refrigerant at a time, as the process monitors forone or more criteria being met, the process 350 will direct (step 358)the refrigerant to a different set of ‘n-x’ evaporator sections 202a-202 n, upon detecting one of the shutdown evaporator sections havingsatisfied one or more of the criteria.

The use of the evaporator 116 combined with the process 350 of FIG. 3B,effectively uses the built-in thermal inertia to increase the TMScooling effectiveness and maintain the temperature tolerances in therange when a undersized cooling system is used.

Referring now to FIG. 4 , an example implementation of a TMS 400 thatincludes an optional OCRS 44 fluidly coupled to a closed-circuitrefrigeration system (CCRS) 40 and one or more evaporators 116 is shown.In this example, TMS 400 provides closed-circuit refrigeration for oneor more low heat loads 120 over long time intervals and open-circuitrefrigeration for refrigeration of one or more high heat loads 118 overshort time intervals (relative to the interval of refrigeration of lowheat load). More specifically, the TMS 400 includes open-circuitrefrigeration system 44, without the optional gas receiver 10 andwithout the control devices 12 and 16, and further includes aclosed-circuit refrigeration system (CCRS) 40.

Optional OCRS 44 includes an open circuit fluid circuit that includes ajunction 410 as well as the components/devices of FIG. 1 , that is thereceiver 110, the optional solenoid valve 112, the expansion valve 114,the evaporator 116, back-pressure regulator 16, exhaust 20, andassociated conduit. The high heat load 118 is in thermal conductiveand/or convective contact with the evaporator 116. The OCRS 44 alsoincludes a suction accumulator 124 having an inlet 125 and a vapor-sideoutlet 127. In some embodiments of TMS discussed herein, the suctionaccumulator 124 is replaced by a liquid separator 124 that also includesa liquid-side outlet (described later) and other conventional featuressuch as membranes, coalescing filters, or meshes, etc. (not shown).

The CCRS 40 (implemented within the TMS 400) includes the receiver 110that includes inlet 109 and outlet 111, the optional solenoid valve 112,the expansion valve 114, the evaporator 116, the suction accumulator124, a junction 410, a compressor 104 having a compressor inlet 101 anda compressor outlet 103, and a condenser 106 having a condenser inlet105 and a condenser outlet 107, all of which are fluidly coupled viaconduit. A fan 108 that generates a condenser airflow 126 (or pump 108that generates a condenser liquid flow 126) cools refrigerant in thecondenser 106. In this example, one or more low heat loads 120 are alsoin thermally conductive and/or convective contact with the evaporator116. The optional solenoid valve 112 can be used when the expansionvalve 114 is not configured to completely stop refrigerant flow when theTMS 400 is in an OFF state.

In some implementations of the CCRS 40, an oil is used for lubricationof the compressor 104 and the oil travels with the refrigerant in theclosed-circuit portion of the TMS 400. The oil is removed from therefrigerant to be recirculated back to the compressor 104. While notexpressly shown, the oil can be removed from the inlet 125 of thesuction accumulator 124, within the suction accumulator 124, orelsewhere within the TMS 400. TMS 400 has a mechanism, e.g., a solenoidvalve (not referenced) and an orifice, to return oil from the suctionaccumulator 124 (or a liquid separator), particularly, from the bottomof the suction accumulator 124 to the compressor 104. In addition, theCCRS 40 may include an oil separator (OS, as shown). The OS is disposedin an oil return path from the compressor outlet 103 to the compressorinlet 101.

TMS 400 cools heat loads 118 and 120 (shown with the evaporator 116).The low heat load 120 is a heat load that operates over long (orcontinuous) time intervals and are cooled by the CCRS 40, whereas thehigh heat load 118 is a heat load that operates over short intervals oftime relative to the operating interval of the low heat load 120.

As shown in this example implementation, TMS 400 includes an optionalsensor 408 in communication with the expansion valve 114. For example,the expansion valve 114 can be operated with sensor 408 that controlsthe expansion valve 114 either directly or through control system 999.The evaporator 116 can operate in two phase (liquid/gas) and superheatedregions with controlled superheat. The electronically-controlledexpansion valve 114 and the sensor 408 provide a mechanism to measureand control superheat.

As further shown in FIG. 4 , TMS 400 can include an optionalrecuperative heat exchanger 402. In some aspects, implementations of theTMS 400 that include recuperative heat exchanger 402 can improve vaporquality at the evaporator 116 exit because of the presence of therecuperative heat exchanger 402 that evaporates any remaining liquidprior to being fed to the inlet 101 of the compressor 104. In someimplementations, the presence of the recuperative heat exchanger 402 caneliminate the need for the suction accumulator 124.

The recuperative heat exchanger 402 is coupled in a first fluid path 404between the outlet 111 and an inlet 401 and between the inlet 113 and anoutlet 405. The recuperative heat exchanger 402 is also coupled in asecond fluid path 406 between the outlet 123 and an inlet 403 andbetween an outlet 407 and the inlet 125 of the suction accumulator 124.The recuperative heat exchanger 402 transfers heat energy from therefrigerant fluid 1 flowing to the suction accumulator 124 torefrigerant fluid 1 upstream from the expansion valve 114. Inclusion ofthe recuperative heat exchanger 402 can reduce mass flow rate demand andallows operation of evaporator 116 within a threshold of vapor quality.In some examples, the recuperative heat exchanger 402 transfers heatenergy from the refrigerant fluid emerging from evaporator 116, and thesuction accumulator 124 is not needed. That is, the recuperative heatexchanger 402 obviates the need for the suction accumulator 124.

Returning now to FIG. 4 , operation of the OCRS 44 is described. Whenthe low heat loads 120 are applied, the TMS 400 is configured to havethe CCRS 40 provide refrigeration to ‘n-x’ of the low heat loads 120. Inthis instance, the control system 999 produces signals to cause theback-pressure regulator 16 to be placed in an OFF state (i.e., closed).With the back-pressure regulator 16 closed, the CCRS 40 provides coolingduty to handle ‘n-x’ of the low loads 120.

In the closed-circuit refrigeration configuration, circulatingrefrigerant enters the compressor 104 as a saturated or superheatedvapor and is compressed to a higher pressure at a higher temperature (asuperheated vapor). This superheated vapor is at a temperature andpressure at which it can be condensed in the condenser 106 by eithercooling water 126 or cooling air 126 flowing across a coil or tubes inthe condenser 106. At the condenser 106, the circulating refrigerantloses heat and thus removes heat from the system, which removed heat iscarried away by either the water 126 or air 126 (whichever may be thecase) flowing over the coil or tubes, providing a condensed liquidrefrigerant.

The condensed and sub-cooled liquid refrigerant fluid 1 is routed intothe receiver 110, exits the receiver 110, and enters the expansion valve114 (if used). The refrigerant fluid is enthalpically expands in theexpansion valve 114 and the high pressure sub-cooled liquid refrigerantturns into liquid-vapor mixture at a low pressure and temperature. Thetemperature of the liquid and vapor refrigerant mixture (evaporatingtemperature) is lower than the temperature of the low heat load 120. Themixture is routed through coils or tubes in ‘n-x’ of the evaporatorsections 202 a-202 n of the evaporator 116. In the evaporator 116, atleast “x” of the evaporator sections 202 a-202 n, is closed, by closingthe corresponding the control valves 204 a-204 n, while refrigerant ispermitted to flow though remaining evaporator sections 202 a-202 n.Process 350, e.g., describes an operation of the evaporator sections 202a-202 n in conjunction with the control valves 204 a-204 n.

The heat from the low heat loads 120 in contact with or proximate to theevaporator sections 202 a-202 n, partially or completely evaporates theliquid portion of the two-phase refrigerant mixture, and may superheatthe mixture. The refrigerant leaves the evaporator 116 and enters thesuction accumulator 124. The saturated or superheated vapor exits thesuction accumulator 124 and enters the compressor 104. The evaporator116 is where the circulating refrigerant absorbs and removes heat fromapplied low heat loads 120, which heat is subsequently rejected in thecondenser 106 and transferred to an ambient by water 126 or air 126 inthe condenser 106. To complete the refrigeration cycle, the refrigerantvapor from the evaporator 116 is stored in the suction accumulator 124and again a saturated vapor portion of the refrigerant in the suctionaccumulator 124 is routed back into the compressor 104.

On the other hand, when a high heat loads 118 are applied, a mechanismsuch as the control system 999 causes the TMS 400 to operate in both aclosed- and open-circuit configurations. The closed-circuit portion issimilar to that described above, except that the evaporator 116 in thiscase operates within a threshold of a vapor quality, e.g., theevaporator 116 may operate with a superheat provided that the liquidseparator captures incidental non-evaporated liquid, the suctionaccumulator 124 receives two-phase mixture, and the compressor 104receives saturated vapor from the suction accumulator 124.

When the TMS 400 operates with the open cycle, this causes the controlsystem 999 to be configured to cause the back-pressure regulator 16 tobe placed in an ON position, thus opening the back-pressure regulator 16to permit the back-pressure regulator 16 to exhaust vapor through theexhaust line 20. The back-pressure regulator 16 maintains a backpressure at an inlet to the back-pressure regulator 16, according to aset point pressure, while allowing the back-pressure regulator 16 toexhaust refrigerant vapor through the exhaust line 20.

The OCRS 44 can operate like a thermal energy storage (TES) system,increasing cooling capacity of the TMS 400 when a pulsing heat load isactivated, but without a duty cycle cooling penalty commonly encounteredwith TES systems. The cooling duty is executed without the concomitantpenalty of conventional TES systems provided that the receiver 110 hasenough refrigerant charge and the refrigerant flow rate flowing throughthe evaporator 116 matches the rate needed by (n-x) of the high heatloads 118. The back-pressure regulator 16 exhausts the refrigerantvapor, less the refrigerant vapor recirculated by the compressor 104.The rate of exhaust of the refrigerant vapor through the exhaust line 20is governed by the set point pressure used at the input to theback-pressure regulator 16. As noted, process 350 describes theoperation of the evaporator sections 202 a-202 n in conjunction with thecontrol valves 204 a-204 n.

When the high heat loads 118 are no longer in use or their temperaturesare reduced, this occurrence is sensed by a sensor (not shown) andsignals from the sensor (or otherwise, such as communicated directly bythe high heat loads 118) are sent to the control system 999. The controlsystem 999 is configured to partially or completely close theback-pressure regulator 16 by changing the set point pressure (orotherwise), partially or totally closing the exhaust line 38 to reduceor cut off exhaust refrigerant flow through the exhaust line 20. Whenthe high heat load 118 reaches a desired temperature or is no longerbeing used, the back-pressure regulator 16 is placed in the OFF statusand is thus closed, and CCRS 40 continues to operate as needed. Theprovision of the CCRS 40 helps to reduce amount of exhaustedrefrigerant.

Generally, the TMS 400 uses the compressor 104 to save, e.g., ammonia,and in general it may not be desirable to shut the compressor 104 off.For instance, the compressor 104 can help to keep a high pressure in thereceiver 110 if a head pressure control valve is applied.

On the other hand, in some embodiments, the TMS 400 could be configuredto operate in modes where the compressor 104 is turned off and the TMS400 operates in open-circuit mode only (such as in fault conditions inthe circuit or cooling requirements).

As noted, the TMS 400 includes the control system 999 that producescontrol signals (based on sensed thermodynamic properties) to controloperation of the various ones of devices as needed, as well as thecompressor 104 and back-pressure regulator 16. Control system 999 mayreceive signals, process received signals and send signals (asappropriate) from/to the expansion valve 114, the optional solenoidvalve 112, and a motor of the compressor 104 changing its speed,shutting compressor 104 off or starting it, etc. As used herein thecompressor 104 is, in general, a device that increases the pressure of agas by reducing the gas' volume. Usually, the term compressor refers todevices operating at and above ambient pressure, (some refrigerantcompressors may operate inducing refrigerant at pressures below ambientpressure, e.g., desalination vapor compression systems employcompressors with suction and discharge pressures below ambient pressure)

Implementations of the TMS 400 that include recuperative heat exchanger402 can adjust a vapor quality of the refrigerant fluid, as therecuperative heat exchanger 402 is configured to generate a sufficientsuperheat and is used with the suction accumulator 124. The vaporquality of the refrigerant fluid after passing through evaporator 116can be controlled either directly or indirectly with respect to a vaporquality set point by the control system 999. The evaporator 116 may beconfigured to maintain exit vapor quality substantially below thecritical vapor quality defined as “1.”

Vapor quality is the ratio of mass of vapor to mass of liquid+vapor andis generally kept in a range of approximately 0.5 to almost 1.0; morespecifically 0.6 to 0.95; more specifically 0.75 to 0.9 morespecifically 0.8 to 0.9 or more specifically about 0.8 to 0.85. “Vaporquality” is thus defined as mass of vapor/total mass (vapor+liquid). Inthis sense, vapor quality cannot exceed “1” or be equal to a value lessthan “0.” In practice vapor quality may be expressed as “equilibriumthermodynamic quality” that is calculated as follows:

X=(h−h′)/(h″−h′),

where h is specific enthalpy, specific entropy or specific volume, h′ isof saturated liquid and “is of saturated vapor. In this case X can bemathematically below 0 or above 1, unless the calculation process isforced to operate differently. Either approach is acceptable.

During operation of the TMS 400, cooling can be initiated by a varietyof different mechanisms. In some embodiments, for example, TMS 400includes temperature sensors attached to heat loads 118 and 120 (as willbe discussed subsequently). When the temperature of heat loads 118 and120 exceeds a certain temperature set point (i.e., threshold value), thecontrol system 999 connected to, e.g., temperature sensors 210, caninitiate cooling of heat loads 118 and 120. Alternatively, in certainembodiments, TMS 400 operates essentially continuously—provided that therefrigerant fluid pressure within receiver 110 is sufficient—to cool lowheat loads 120 and a temperature sensor attached to high heat loads 118will cause the control system 999 to switch in the OCRS 44 when thetemperatures of high heat loads 118 exceed temperature set point (i.e.,threshold value). As soon as receiver 110 is charged with refrigerantfluid 1, refrigerant fluid 1 is ready to be directed into evaporator 116to cool heat loads 118 and 120. In general, cooling is initiated when auser of the system or the heat load issues a cooling demand.

Referring now to FIG. 5 , an example implementation of a TMS 500 thatincludes an OCRS 54 fluidly coupled to a CCRS 50 with an ejector assistcircuit 52 and one or more evaporators 116 is shown. TMS 500 can alsoimplement the process 300 that applies power to all of the heat loads118 and 120 in the precooled evaporator sections 202 a-202 n, causingthe heat loads 118 and 120 to operate under normal circumstances. Insome aspects, the use of the ejector assist circuit 52 can assist inreducing a power requirement of the TMS 500. Items illustrated andreferenced, but not mentioned in the discussion below, are discussed andreferenced in FIG. 1 and FIG. 4 .

As shown in FIG. 5 , the TMS 500 includes the OCRS 54 integrated withthe CCRS 50. The OCRS 54 is an ejector assisted open circuitrefrigeration system. The CCRS 50 generally, includes ejector assistcircuit 52 and a liquid separator 124 with a vapor section 522 and aliquid section 524 rather than a suction accumulator. The CCRS 50provides cooling for low heat load 120 over long time intervals whilethe OCRS 54 provides cooling for high heat load 118 over short timeintervals, as generally discussed above.

TMS 500 includes the receiver 110 that is configured to store sub-cooledliquid refrigerant, as discussed above, and may include an optionalsolenoid valve 112 and optional expansion valve 114. Both, either orneither of the optional solenoid valve 112 and the optional expansionvalve 114 can be used (i.e., or not used) in example embodiments of theTMS 500.

The TMS 500 includes an ejector 502. The ejector 502 has a primary inlet(i.e., high pressure inlet) 501 that is coupled to the receiver 110(either directly or through the optional solenoid valve 112 and/orexpansion valve 114). Outlet 505 of the ejector 502 is coupled to theinlet 125 of the liquid separator 124 (through a evaporator 116 in thisexample, as explained more fully below). The ejector 502 also has asecondary inlet or low-pressure inlet 503 that is coupled to theliquid-side outlet 527 via the evaporator 116. The vapor-side outlet 127of the liquid separator 124 is coupled to the junction 410 that iscoupled to the back-pressure regulator 16. The back-pressure regulator16 has an outlet (not referenced) that feeds exhaust line 20. Thejunction 410 is coupled to the inlet 101 of the compressor 104. Theoutlet 103 of the compressor 104 is coupled to the inlet 105 of thecondenser 106.

In some aspects, ejector 502 includes a high-pressure motive nozzle orprimary inlet 501, a suction or secondary inlet 503, a secondary nozzlethat feeds a suction chamber, a mixing chamber for the primary flow ofrefrigerant and secondary flow of refrigerant to mix, and a diffuser. Inone embodiment, the ejector 502 is passively controlled by built-in flowcontrol. Also, optional flow control devices may be employed upstream ofthe ejector 502. Liquid refrigerant from the receiver 110 is the primaryflow. In the motive nozzle, potential energy of the primary flow isconverted into kinetic energy reducing the potential energy (theestablished static pressure) of the primary flow. The secondary flowfrom the outlet 123 of the evaporator 116 (or from the liquid outlet527) has a pressure that is higher than the established static pressurein the suction chamber, and thus the secondary flow is entrained throughthe suction inlet 503 and the secondary nozzles internal to the ejector502. The two streams (primary flow and secondary flow) mix together inthe mixing chamber. In the diffuser section, the kinetic energy of themixed streams is converted into potential energy elevating the pressureof the mixed flow liquid/vapor refrigerant that leaves the ejector 502and is fed to the inlet 121 of the evaporator 116 (or liquid separator124). In the context of open-circuit refrigeration systems, the use ofthe ejector 502 allows for recirculation of liquid refrigerant capturedby the liquid separator 124 to increase the efficiency of the TMS 500.That is, by allowing for some recirculation of refrigerant, but withoutthe need for a compressor or a condenser, this recirculation reduces therequired amount of refrigerant needed for a given amount of cooling of‘n-x’ high heat loads 118 over given periods of operation.

An evaporator 116 is coupled between the ejector outlet 505 of theejector 502 and the inlet 125 of the liquid separator 124 in thisexample ejector assist circuit 52. In this configuration, an evaporator116 is coupled between the ejector outlet 505 and the liquid separatorinlet 125. The flow control device 130 is coupled between the secondaryinlet 503 of the ejector 502 and the liquid-side outlet 527 of theliquid separator 124. The recirculation rate in this example is equal tothe vapor quality at the evaporator outlet. The flow control device 130is optional, and when used, is a fixed orifice device. The expansionvalve 114 or other control device can be built in the motive nozzle ofthe ejector 502 and provides active control of the thermodynamicparameters of refrigerant state at the outlet 123. By placing theevaporator 116 between the outlet 505 of the ejector 502 and the inlet125 of the liquid separator 124, the necessity of having liquidrefrigerant pass through the liquid separator 124 during the initialcharging of the evaporator 116 with the liquid refrigerant is avoided.At the same time liquid trapped in the liquid separator 124 may bewasted after the TMS 500 shuts down.

In this example configuration, the recirculation rate is equal to thevapor quality at the outlet 123 of the evaporator 116. The flow controldevice 530 is optional, and when used, can be a fixed orifice device.The expansion valve 114 or other control device can be built in themotive nozzle of the ejector 502 and provides active control of thethermodynamic parameters of refrigerant state at the outlet 123 of theevaporator 116.

In an alternative example of the ejector assist circuit 52 of the TMS500, the evaporator 116 can be fluidly coupled such that the inlet 121is connected to liquid outlet 527 of the liquid separator (e.g., throughjunction 504) and the outlet 123 is fluidly coupled to the secondaryinlet 503 of the ejector 502 (as shown in the dashed line representationof evaporator 116). For example, the evaporator 116 can be coupled tothe secondary inlet 503 of the ejector 502 and to junction 504, suchthat the control device 130 and conduit couple the evaporator 116 to theliquid-side outlet 527 of the liquid separator 124.

During open circuit operation in such a configuration, the ejector 502again acts as a “pump,” to “pump” a secondary fluid flow, e.g.,liquid/vapor from the evaporator 116 using energy of the primaryrefrigerant flow from the receiver 110. The evaporator 116 may beconfigured to maintain exit vapor quality below the critical vaporquality defined as “1.” However, the higher the exit vapor quality thebetter it is for operation of the ejector 502. Vapor quality is theratio of mass of vapor to mass of liquid+vapor and is generally kept ina range of approximately 0.5 to almost 1.0; more specifically 0.6 to0.95; more specifically 0.75 to 0.9 more specifically 0.8 to 0.9 or morespecifically about 0.8 to 0.85. In such a configuration, refrigerantfrom receiver 110 enters into the primary inlet 501 of the ejector 502and through the ejector assist circuit 52, meaning that refrigerantflows from the ejector 502 into liquid separator 124 and flow from theliquid separator 124 is expanded by the flow control device 530 (as anexpansion valve) into the evaporator 116, which cools the heat loads 118and/or 120. The refrigerant is returned to the ejector 502 and to theliquid separator 124, while a vapor fraction of the refrigerant is fedto the compressor 104 and to the condenser 106. The liquid separator 124is used to insure only vapor exists at the input to the compressor 104.In this embodiment, an optional sensor can be disposed at the outlet 123of the evaporator 116 and communicably coupled to the flow controldevice 530 (as an expansion valve). The expansion valve 130 and sensorprovide a mechanism to measure and control superheat. Closed circuit andopen circuit operate as generally discussed for TMS 500, except forprovision of the sensor 932 to measure and control superheat.

Further, in another alternative example of the ejector assist circuit 52of the TMS 500, dual evaporators 116 can be installed in the ejectorassist circuit 52 (i.e., with both the solid line and dashed linerepresentations of the evaporator 116 in FIG. 5 included). In such anexample, a evaporator 116 is coupled between outlet 505 of the ejector502 and inlet 125 to the liquid separator 124 and another evaporator 116is coupled between an outlet of the flow control device 130 andsecondary inlet 503 to the ejector 502. Heat loads 118 and/or 120 arecoupled to both evaporators 116. The cooling capacity of thisconfiguration of TMS 500 may not be sensitive to recirculation rate (ascompared to other example implementations), which may be beneficial whenthe heat loads may significantly reduce recirculation rate. An operatingadvantage of such a configuration is that by using dual evaporators 116,it is possible to run the evaporators 116 combining the features of theconfigurations mentioned above. Also, in this configuration, at leastone evaporator 116 can operate with both high heat load 118 and low heatload 120 if those loads allow for operation in superheated regions.

Further, in another alternative example of the ejector assist circuit 52of the TMS 500, the evaporator 116 can comprise a single evaporator 116that is attached downstream from and upstream of the ejector 502.

In this example of the TMS 500, an optional evaporator circuit 56 isfluidly coupled at junction 504 to the ejector assist circuit 52 throughoptional flow control valve 530 (e.g., expansion valve 530). In thisoptional circuit 56, a conventional evaporator 516 (e.g., not a gatingevaporator) is disposed within exhaust 528 with an inlet 521 coupled tothe expansion valve 530 and an outlet 523 with a back-pressure regulator526. The conventional evaporator 516 is in thermal conductive and/orconvective contact with heat load 518. Optionally in the optionalevaporator circuit 56 is a sensor communicably coupled to the flowcontrol device 530 (as an expansion valve). The conventional evaporator516 can operate in a superheated region with controlled superheat by theexpansion valve 530, which has a control port that is fed from a sensor.The sensor controls the expansion valve 530 and provides a mechanism tomeasure and control superheat.

If the optional expansion valve and sensor are not included with theoptional evaporator circuit 56, then the conventional evaporator 516shares the same control device 530, i.e., an expansion valve, as theevaporator 116 (or evaporators 116 in the case of dual evaporators 116).

The evaporator(s) 116 operates in two-phase (liquid/gas) andconventional evaporator 516 operates in a superheated region withcontrolled superheat.

In some embodiments, refrigerant flow through the TMS 500 duringopen-circuit operation is controlled in the OCRS 54 either solely by theejector 502 and back-pressure regulator 16 or by those components aidedby either one or all of the optional solenoid valve 112 and expansionvalve 114, depending on requirements of application, e.g., ranges ofmass flow rates, cooling requirements, receiver capacity, ambienttemperatures, heat load, etc. and the flow control device 530.

While both expansion valve 114 and solenoid valve 112 may not typicallybe used, in some implementations, either or both would be used and wouldfunction as a flow control device(s) to control refrigerant flow intothe primary inlet 501 of the ejector 502. In some embodiments, theexpansion valve 114 can be integrated with the ejector 502. In variousembodiments of the TMS 500, the optional expansion valve 114 may berequired under some circumstances where there are or can be significantchanges in, e.g., an ambient temperature, which might impose additionalcontrol requirements on the TMS 500.

The back-pressure regulator 16 has an outlet (not referenced) that isdisposed at the exhaust line 20, and further has an inlet (notreferenced) coupled via junction 410 to the vapor-side outlet 127 of theliquid separator 124. The back-pressure regulator 16 functions tocontrol the vapor pressure upstream of the back-pressure regulator 16.In TMS 500, the back-pressure regulator 16 is a control device thatcontrols the refrigerant fluid vapor pressure from the liquid separator124 and indirectly controls evaporating pressure/temperature when theTMS 500 is operating in open circuit mode. In general, back-pressureregulator 16 can be implemented using a variety of different mechanicaland electronic flow regulation devices, as mentioned above. Theback-pressure regulator 16 regulates fluid pressure upstream from theregulator, i.e., regulates the pressure at the inlet to theback-pressure regulator 16 according to a set pressure point value.

Regarding closed-circuit refrigeration, the CCRS 50 generally operatesas discussed above in FIG. 4 , with addition of the circuit 52 providedby the ejector 502, liquid separator 124, and evaporator 116. The CCRS50 provides cooling for low heat loads 120 over long time intervals. Theejector 502 acts as a “pump,” to “pump” a secondary fluid flow, e.g.,liquid/vapor from the evaporator 116 (or to the evaporator 116, or both)using energy of the primary refrigerant flow from the receiver 110.

In some embodiments, refrigerant flow through the ejector assist circuit52 and OCRS 54, during open-circuit operation, is controlled eithersolely by the ejector 502 and back-pressure regulator 16 or by thosecomponents aided by either one or all of the solenoid valve 112 andexpansion valve 114, depending on requirements of application, e.g.,ranges of mass flow rates, cooling requirements, receiver capacity,ambient temperatures, thermal load, etc. and the flow control device530.

While both expansion valve 114 and solenoid valve 112 may not typicallybe used, in some implementations, either or both would be used and wouldfunction as a flow control device(s) to control refrigerant flow intothe primary inlet 66 a of the ejector 502. In some embodiments, theexpansion valve 114 is an expansion valve and can be integrated with theejector 502. In various embodiments of the TMS 500, the optionalexpansion valve 530 may be required under some circumstances where thereare or can be significant changes in, e.g., an ambient temperature,which might impose additional control requirements on the TMS 500.

The back-pressure regulator 16 has an outlet (not referenced) that isdisposed at the exhaust line 20, and further has an inlet (notreferenced) coupled via junction 410 to the vapor side outlet 127 of theliquid separator 124. The back-pressure regulator 16 functions tocontrol the vapor pressure upstream of the back-pressure regulator 16.

Some loads require maintaining thermal contact between the loads 118 andevaporator 116 with the refrigerant being in the two-phase region (of aphase diagram for the refrigerant) and, therefore, the flow controldevice 530 maintains a proper vapor quality at the evaporator outlet123. Alternatively, a sensor communicating with control system 999 maymonitor pressure in the receiver 110, as well as a pressure differentialacross the expansion valve 114, a pressure drop across the evaporator116, a liquid level in the liquid separator 124, and power input intoelectrically actuated heat loads, or a combination of above.

In the configuration as shown (e.g., with only the evaporator 116 insolid line representation), the evaporator 116 is coupled between theejector outlet 505 and the liquid separator inlet 125. The flow controldevice 530 is coupled between the secondary inlet 503 of the ejector 502and the liquid side outlet 527 of the liquid separator 124. Theevaporator 116 is configured to extract heat from the heat loads 118 and120 that are in thermal conductive and/or convective contact or inproximity to the evaporator 116.

In TMS 500 in this configuration, the recirculation rate is equal to thevapor quality at the evaporator outlet 123. The flow control device 530is optional, and when used, can be a fixed orifice device. The expansionvalve 114 or other control device can be built in the motive nozzle ofthe ejector 502 and provides active control of the thermodynamicparameters of refrigerant state at the evaporator outlet 123.

This embodiment of the TMS 500 operates as follows, with theback-pressure regulator 16 in a closed or off position. Refrigerantfluid 1 from the receiver 110 is directed into the ejector 512(optionally through valve 112 and expansion valve 114) and expands at aconstant entropy in the ejector 502 (in an ideal case; in reality thenozzle is characterized by the ejector isentropic efficiency), and turnsinto a two-phase (gas/liquid) state. The refrigerant in the two-phasestate enters the evaporator 116 that provides cooling duty (to ‘n-x’ ofheat loads 118 and 120) and discharges the refrigerant in a two-phasestate at an exit vapor quality (fraction of vapor to liquid) below aunit vapor quality (“1”). The discharged refrigerant is fed to the inlet125 of the liquid separator 124, where the liquid separator 124separates the discharge refrigerant with only or substantially onlyliquid exiting the liquid separator 124 at the liquid side outlet 527and only or substantially only vapor exiting the separator 124 at thevapor side outlet 127. The vapor section 522 may contain some liquiddroplets since the liquid separator 124 has a separation efficiencybelow a “unit” separation. The liquid stream exiting at outlet 527(through junction 504) enters the suction or secondary inlet 505 of theejector 502. The ejector 502 entrains the refrigerant flow exiting theexpansion valve by the refrigerant from the receiver 110.

In closed-circuit operation, back-pressure regulator 16 is turned offand vapor from the liquid separator 124 is fed to the compressor 104 andcondenser 106, as generally discussed above. In open-circuit operation,back-pressure regulator 16 is turned on and a portion of the vapor isexhausted through exhaust line 20, as generally discussed above.

In TMS 500, by placing the evaporator 116 between the outlet 505 of theejector 502 and the inlet 125 of the liquid separator 124, TMS 500avoids the necessity of having liquid refrigerant pass through theliquid separator 124 during the initial charging of the evaporator 116with the liquid refrigerant. At the same time, liquid trapped in theliquid separator 124 may be wasted after the TMS 500 shuts down.

When the evaporator 116 is fluidly coupled at inlet 121 to the junction504 and at the outlet 123 to the secondary inlet 503 of the ejector 502,operation may commence as follows. For example, during open-circuitoperation, the ejector 502 again acts as a “pump,” to “pump” a secondaryfluid flow, e.g., liquid/vapor from the evaporator 116 using energy ofthe primary refrigerant flow from the receiver 110.

The evaporator 116 may be configured to maintain exit vapor qualitybelow the critical vapor quality defined as “1.” However, the higher theexit vapor quality the better it is for operation of the ejector 502.Vapor quality is the ratio of mass of vapor to mass of liquid+vapor andis generally kept in a range of approximately 0.5 to almost 1.0; morespecifically 0.6 to 0.95; more specifically 0.75 to 0.9 morespecifically 0.8 to 0.9 or more specifically about 0.8 to 0.85, asdiscussed above.

The CCRS 50, in this configuration, operates as above, except thatrefrigerant from receiver 110 enters into the primary inlet 501 of theejector 502 and through the circuit 52, meaning that refrigerant flowsfrom the ejector 502 into liquid separator 124 and refrigerant flow fromthe liquid separator 124 is expanded by the flow control device 16 intothe evaporator 116, which cools heat load 118. The refrigerant isreturned to the ejector 502 and to the liquid separator 26, while avapor fraction of the refrigerant is fed to the compressor 104 and tothe condenser 106, as discussed above. The liquid separator 124 is usedto insure only vapor exists at the inlet 101 to the compressor 104.

The OCRS 54 operates as follows. The liquid refrigerant from thereceiver 110 (primary flow) is fed to the primary inlet 501 of theejector 502 and expands at a constant entropy in the ejector 502 (inideal case; in reality the nozzle is characterized by the isentropicefficiency of the ejector) and turns into a two-phase (gas/liquid)state. The refrigerant in the two-phase state from the ejector 502enters the liquid separator 124, at inlet port 125 with only orsubstantially only liquid exiting the liquid separator 124 at the liquidside outlet 527 and only or substantially only vapor exiting theseparator 124 at vapor side outlet 127.

The evaporator 116 provides cooling duty and discharges the refrigerantin a two-phase state at relatively low exit vapor quality (low fractionof vapor to liquid, e.g., generally below 0.5) into the secondary inlet503 of the ejector 502. The ejector 502 entrains the refrigerant flowexiting the evaporator 116 and combines it with the primary flow fromthe receiver 110. Vapor exits from the vapor side outlet 127 of theliquid separator 124 and is exhausted by the exhaust line 20. Theback-pressure regulator 16, regulates the pressure upstream of theregulator 16 so as to maintain upstream refrigerant fluid pressure inTMS 500.

In the case of dual evaporators 116 (as previously described) in TMS500, such a configuration may not be sensitive to recirculation rates(as compared to single evaporator configurations), which may bebeneficial when the heat loads may significantly reduce recirculationrate. An operating advantage of a dual evaporator 116 configuration isthat by placing evaporators 116 at both the outlet 505 and the secondaryinlet 503 of the ejector 502, it is possible to run the evaporators 116combining the features of the configurations mentioned above. Also, inthis configuration, evaporator 116 (in dashed line) can operate withheat loads 118 and 120 if those loads allow for operation in superheatedregions.

Referring now to FIG. 6 , an example implementation of a TMS 600 thatincludes an OCRS 64 fluidly coupled to a CCRS 60 with a pump assistcircuit 62 and one or more evaporators 116 is shown. TMS 600 can alsoimplement the processes 300/350 that applies power to all of the heatloads 118 and 120 in the precooled evaporator sections 202 a-202 n,causing the heat loads 118 and 120 to operate under normalcircumstances. In some aspects, the use of the pump assist circuit 62can assist in reducing a power requirement of the TMS 600. Itemsillustrated and referenced, but not mentioned in the discussion below,are discussed and referenced in FIG. 1 , FIG. 4 , and FIG. 5 .

As shown in FIG. 6 , the TMS 600 includes the OCRS 64 integrated withthe CCRS 60. The OCRS 64 is an pump assisted open circuit refrigerationsystem. The CCRS 50 generally, includes pump assist circuit 52 andliquid separator 124 with a vapor section 522 and liquid section 524rather than a suction accumulator. The CCRS 60 provides cooling for lowheat load 120 over long time intervals while the OCRS 64 providescooling for high heat load 118 over short time intervals, as generallydiscussed above.

TMS 600 includes the receiver 110 that is configured to store liquidrefrigerant, i.e., subcooled liquid refrigerant, optional solenoidcontrol valve 112, optional expansion valve 114, and a junction 604 thathas first and second ports configured as inlets and a third portconfigured as an outlet. TMS 600 also includes one or more evaporators116, liquid separator 124, a pump 602 having inlet 601 and outlet 603,back-pressure regulator 16, and exhaust line 20. TMS 600 also includescompressor 104 and the condenser 106 having the outlet 107 coupled tothe inlet 109 of receiver 110. The TMS 600 includes pump assist circuit62 having the junction 604, one or more evaporators 116, the liquidseparator 124, and the pump 602.

The junction 604 has the first port coupled to the receiver 110 (e.g.,through optional valve 112 and expansion valve 114), the second port asan inlet coupled to the outlet 123 of the evaporator 116 (shown in solidline), and a third port as the outlet coupled to the inlet 125 of theliquid separator 124 (through an optional second evaporator 116).

The liquid separator 124 has the inlet 125, the vapor-side outlet 127and liquid-side outlet 527. The vapor-side outlet 127 of the liquidseparator 124 is coupled via junction 410 to inlet 102 of the compressor104 that controls a vapor pressure in the evaporator 116 and feeds vaporto the condenser 106. The vapor-side outlet 127 is coupled to one portof the junction 410 that feeds compressor 104 and the back-pressureregulator 16. The back-pressure regulator 16 has an outlet that feedsexhaust line 20. The liquid-side outlet 527 of the liquid separator 124is coupled to inlet 601 of the pump 602 (as shown in this example).

The liquid separator 124 and pump 602 can be arranged in several exampleconfigurations. For example, the liquid separator 124 (e.g., implementedas a flash drum) can have the pump 602 located distal from theliquid-side port 527 as shown in FIG. 6 . This configuration potentiallypresents the possibility of cavitation. To minimize the possibility ofcavitation, the pump 602 can be located distal from the liquid-sideoutlet port 527, but the height at which the inlet 125 is located ishigher than conventional. This would result in an increase in liquidpressure at the liquid-side outlet 527 of the liquid separator 124 andconcomitant therewith an increase in liquid pressure at the inlet 601 ofthe pump 602. Increasing the pressure at the inlet 601 to the pump 602should minimize possibility of cavitation. Another strategy is to locatethe pump 602 proximate to or indeed, inside of the liquid-side outlet527. In addition, the height at which the inlet 125 is located can beadjusted increase liquid pressure at the inlet 601 of the pump 602further minimizing the possibility of cavitation. Another alternativestrategy that can be used for any of the configurations involves the useof a sensor that produces a signal that is a measure of the height of acolumn of liquid in the liquid separator 124. The signal is sent to thecontrol system 999 that will be used to start the pump 602, once asufficient height of liquid is contained by the liquid separator 124.

Various types of pumps can be used for pump 602. Exemplary types includegear, centrifugal, rotary vane types. When choosing a pump, the pumpshould be capable to withstand the expected fluid flows, includingcriteria such as temperature ranges for the fluids, and materials of thepump should be compatible with the properties of the fluid. A subcooledrefrigerant can be provided at the pump outlet 603 to avoid cavitation.To do that a certain liquid level in the liquid separator 124 mayprovide hydrostatic pressure corresponding to that sub-cooling.

The junction 604 can positioned in several example positions in the pumpassist circuit 62. For example, one of the inlets and the outlet can beinterposed between solenoid valve 112 and expansion valve 114, with itsother inlet coupled to the outlet 123 of the evaporator 116 (shown insolid line). As another example, one of the inlets and the outletinterposed between the outlet 119 of the expansion valve 114 and inlet121 to the evaporator 116 (shown dashed line) or inlet 125 to liquidseparator 124, with its other inlet coupled to the outlet 123 of theevaporator 116 (shown in solid line). As another example, if both of theoptional solenoid control valve 112 and optional expansion valve 114 arenot included, then all of the locations for the junction 604 are, inessence, the same provided that there are no other interveningfunctional devices between the outlet 111 of the receiver 110 and theinlet of the junction 604.

In TMS 600, refrigerant liquid from the liquid-side outlet 527 of theliquid separator 124 is fed to pump inlet 601 and is pumped from thepump 602 into the inlet 121 of the evaporator 116. Refrigerant exitingfrom the outlet 123 is fed along with the primary refrigerant flow fromthe expansion valve 114 back to the liquid separator 124 (throughanother evaporator 116 as an option as shown). These liquid refrigerantstreams from the receiver 110 and the pump 602 are mixed downstream fromthe expansion device 114. Heat loads 118 and/or 120 are in thermalconductive and/or convective contact with or in proximity to theevaporator 116 (or dual evaporators 116 as shown). The evaporator 116 isconfigured to extract heat from the heat loads 118 and/or 120 and tocontrol the vapor quality at the outlet 123 of the evaporator 116.

The evaporator 116 is coupled between the pump outlet 603 of the pump602 and the junction 604 in this example pump assist circuit 62. In analternative example of TMS 600, there can be dual evaporators 116 (withone shown in solid line in FIG. 6 and another evaporator 116 shown indashed line as an option). Thus, in this example modification, a firstevaporator 116 is coupled between the outlet of the junction 604 and theinlet 125 of the liquid separator 124 (as shown in dashed line) andthere is a second evaporator 116 having an inlet 121 that is coupled tothe outlet 603 of the pump 602 and having an outlet 123 coupled to asecond inlet of the junction 604 (this evaporator 116 being shown insolid line). The liquid separator 124 has the inlet 125, the vapor-sideoutlet 127 and liquid-side outlet 527. Heat loads 118 and/or 120 are inthermal conductive and/or convective contact or in proximity to bothevaporators 116 in this modified example. An operating advantage of thismodified example is that by placing evaporators 116 at both the outletand the second inlet of the junction 604, it is possible to combine heatloads 118 and 120 at both evaporators 116, which requires operation in atwo-phase region and which allows operation with superheat.

An operating advantage of the dual evaporator configuration is that itis possible to run the evaporators 116 with changing refrigerant ratesthrough the junction 604 to change at different temperatures or changerecirculating rates. By using the evaporators 116, the configurationreduces vapor quality at the outlet 123 of the evaporator 116 (shown insold line) and thus increases circulation rate, as the pump 602 would be‘pumping’ less vapor and more liquid. That is, with the evaporator 116(in solid line) is downstream from the pump 602 and better refrigerantdistribution could be provided with this component configuration sinceliquid refrigerant enters the evaporator 116 (in solid line) rather thana liquid/vapor stream as could be for the evaporator 116 (in dashedline). In addition, some heat loads that may be cooled by an evaporatorin the superheated phase region, at the same time do not need toactively control superheat.

Further, in another alternative example of the pump assist circuit 62 ofthe TMS 600, the evaporator 116 can comprise a single evaporator 116that is attached downstream from and upstream of the junction 604. Forexample, as a single evaporator 116, the evaporator 116 has a firstinlet 121 that is coupled to the outlet of the junction 604 and a firstoutlet 123 that is coupled to the inlet 125 of the liquid separator 124.The evaporator 116 also has a second inlet 121 that is coupled to theoutlet 603 of the pump 602 and has a second outlet 123 that is coupledto the inlet of the junction 604. The liquid-side outlet 527 of theliquid separator 124 is coupled to the inlet 601 of the pump 602.

In this example implementation, optional evaporator circuit 66 isfluidly coupled to the liquid separator 124. For example, as shown, inthis optional configuration, the liquid separator 124 is configured tohave a second, liquid-side outlet 605 in addition to the inlet 125, thevapor-side outlet 127, and the liquid-side outlet 527. Alternatively,such a function could be provided with another junction (not shown). Thesecond outlet 605 diverts a portion of the liquid exiting the liquidseparator 124 into a conventional evaporator 616 (with inlet 621 andoutlet 623) that is in thermal contact with heat load 618. Theconventional evaporator 616 extracts heat from the heat load 618 andexhausts vapor from exhaust line 630.

Exhaust lines 20 and 630 can be combined or can be separated. As shownin the optional evaporator circuit 66, in the case of exhaust 630 notbeing combined with exhaust 20, another back-pressure regulator 620 canbe placed in the exhaust 630.

The evaporator circuit 66 can cool heat loads in two-phase andsuperheated regions. The conventional evaporator 616 can be fed aportion of the liquid refrigerant and operate in superheated regionwithout the need for active superheat control. For example, optionallyin the optional evaporator circuit 66 is expansion valve 614 and sensor640. The conventional evaporator 616 operates in a superheated regionwith controlled superheat by the expansion valve 614, which has acontrol port that is fed from sensor 640. The sensor 640 controls theexpansion valve 614 and provides a mechanism to measure and controlsuperheat.

The sensor 640 disposed proximate to the outlet 623 of the conventionalevaporator 616 provides a measurement of superheat, and indirectly,vapor quality. For example, sensor 640 is a combination of temperatureand pressure sensors that measures the refrigerant fluid superheatdownstream from the heat load 618 and transmits the measurements to thecontrol system 999. The control system 999 adjusts the expansion valve614 based on the measured superheat relative to a superheat set pointvalue. By doing so, control system 999 indirectly adjusts the vaporquality of the refrigerant fluid emerging from conventional evaporator616.

In closed—circuit operation, the CCRS 60 operates as follows. Theback-pressure regulator 16 is placed in an OFF position. The liquidrefrigerant from the receiver 110 is fed to the expansion valve 114 (ifused) and expands at a constant enthalpy in the expansion valve 114turning into a two-phase (gas/liquid) mixture. This two-phaseliquid/vapor refrigerant is fed to the inlet 125 of the liquid separator124 (or in the case of dual evaporators, the evaporator 116 shown indashed line), where the liquid separator 124 separates the dischargerefrigerant with only or substantially only liquid exiting the liquidseparator 124 at the liquid-side outlet 527 (or both outlet 527 andoutlet 655 in the case of the optional evaporator circuit 616) and onlyor substantially only vapor exiting the liquid separator 124 atvapor-side outlet 127. The liquid stream exiting at liquid-side outlet527 enters and is pumped by the pump 602 into the evaporator 116 thatprovides cooling duty and discharges the refrigerant in a two-phasestate at a relatively high exit vapor quality (fraction of vapor toliquid). The discharged refrigerant is fed to the junction 604. Vaporfrom the vapor-side 127 of the liquid separator 124 is fed to thecompressor 104, on to the condenser 106, and back into the receiver 110for closed circuit operation.

On the other hand, when high heat load 118 is applied, a mechanism suchas the control system 999 causes the TMS 600 to operate in both a closedand open cycle configuration. The closed cycle portion would be similarto that described. The OCRS 64 has the control system 999 configured tocause the back-pressure regulator 16 to be placed in an ON position,opening the back-pressure regulator 16 to permit the back-pressureregulator 16 to exhaust vapor through the exhaust line 20. Theback-pressure regulator 16 maintains a back-pressure at an inlet to theback-pressure regulator 16, according to a set point pressure, whileallowing the back-pressure regulator 16 to exhaust refrigerant vapor tothe exhaust line 20.

In OCRS 64, the pump 602 can operate across a reduced pressuredifferential (pressure difference between inlet 601 and outlet 603 ofthe pump 602). In the context of open circuit refrigeration systems, theuse of the pump 602 allows for recirculation of liquid refrigerant fromthe liquid separator 124 to enable operation at reduced vapor quality atthe evaporator outlet 123, avoiding the discharge of remaining liquidout of the TMS 600 at less than the separation efficiency of the liquidseparator 124 allows. This recirculation reduces the required amount ofrefrigerant needed for a given amount of cooling over a given period ofoperation. The configuration above reduces the vapor quality at theevaporator inlet 121 and thus may improve refrigerant distribution (ofthe two-phase mixture) in the evaporator 116.

Generally, and as discussed with reference to FIGS. 4, 5, and 6 , byadjusting the pressure pc of the refrigerant fluid 1, the temperature atwhich the liquid refrigerant phase undergoes vaporization withinevaporator 116 can be controlled. Thus, in general, the temperature ofheat loads 118, 120 can be controlled by a device or component of a TMSthat regulates the pressure of the refrigerant fluid within evaporator116. System operating parameters include the superheat and the vaporquality of the refrigerant fluid emerging from evaporator 116.

The vapor quality, which is a number from 0 to 1, represents thefraction of the refrigerant fluid that is in the vapor phase.Considering the high heat load 118 individually, because heat absorbedfrom heat load 118 is used to drive a constant-temperature evaporationof liquid refrigerant to form refrigerant vapor in an evaporator sectionof the evaporator 116, it is generally important to ensure that, for aparticular volume of refrigerant fluid propagating through evaporator116, at least some of the refrigerant fluid remains in liquid form rightup to the point at which the exit aperture of an evaporator section inthe evaporator 116 is reached to allow continued heat absorption fromheat load 118 without causing a temperature increase of the refrigerantfluid. If the fluid is fully converted to the vapor phase afterpropagating only partially through evaporator 116, further heatabsorption by the (now vapor-phase) refrigerant fluid within evaporator116 will lead to a temperature increase of the refrigerant fluid andheat load 118.

On the other hand, liquid-phase refrigerant fluid that emerges fromevaporator 116 represents unused heat-absorbing capacity, in that theliquid refrigerant fluid did not absorb sufficient heat from the highheat load 118 to undergo a phase change. To ensure that a TMS operatesefficiently, amount of unused heat-absorbing capacity should remainrelatively small.

In addition, the boiling heat transfer coefficient that characterizesthe effectiveness of heat transfer from the high heat load 118 to therefrigerant fluid is typically very sensitive to vapor quality. When thevapor quality increases from zero to a certain value, called a criticalvapor quality, the heat transfer coefficient increases. When the vaporquality exceeds the critical vapor quality, the heat transfercoefficient is abruptly reduced to a very low value, causing dryoutwithin evaporator 116. In this region of operation, the two-phasemixture behaves as superheated vapor.

In general, the critical vapor quality and heat transfer coefficientvalues vary widely for different refrigerant fluids, and heat and massfluxes. For all such refrigerant fluids and operating conditions, thesystems and methods disclosed herein control the vapor quality at theoutlet of the evaporator such that the vapor quality approaches thethreshold of the critical vapor quality.

To make maximum use of the heat-absorbing capacity of the two-phaserefrigerant fluid mixture for high heat load 118, the vapor quality ofthe refrigerant fluid emerging from evaporator 116 should nominally beequal to the critical vapor quality. Accordingly, to both efficientlyuse the heat-absorbing capacity of the two-phase refrigerant fluidmixture and also ensure that the temperature of heat load 118 remainsapproximately constant at the phase transition temperature of therefrigerant fluid in evaporator 116, the systems and methods disclosedherein are generally configured to adjust the vapor quality of therefrigerant fluid emerging from evaporator 116 to a value that is lessthan or equal to the critical vapor quality.

Another important operating consideration for a TMS is the mass flowrate of refrigerant fluid within the TMS. A gated evaporator 116 can beconfigured to provide minimal mass flow rate controlling maximal vaporquality, which is the critical vapor quality. By minimizing the massflow rate of the refrigerant fluid according to the cooling requirementsfor high heat loads 118, a TMS operates efficiently. Each reduction inthe mass flow rate of the refrigerant fluid (while maintaining the sametemperature set point value for high heat loads 118) means that thecharge of refrigerant fluid added to receiver 110 initially lastslonger, providing further operating time for a TMS.

Within evaporator 116, the vapor quality of a given quantity ofrefrigerant fluid varies from an evaporator inlet (where vapor qualityis lowest) to an evaporator outlet (where vapor quality is highest).Nonetheless, to realize the lowest possible mass flow rate of therefrigerant fluid within the system, the effective vapor quality of therefrigerant fluid within evaporator 116—even when accounting forvariations that occur within evaporator 116—should match the criticalvapor quality as closely as possible.

CCRS power demand and CCRS efficiency are optimal when the evaporatingtemperature is as high as possible and the condensing pressure is as lowas possible. The condenser 106 and evaporator 116 dimensions can bereduced when the evaporating temperature is as low as possible and thecondensing pressure is as high as possible.

To ensure that an OCRS operates efficiently and the mass flow rate ofthe refrigerant fluid is relatively low, and at the same time thetemperature of the high heat load 118 is maintained within a relativelysmall tolerance, a TMS adjusts the vapor quality of the refrigerantfluid emerging from evaporator 116 to a value such that an effectivevapor quality within evaporator 116 matches, or nearly matches, thecritical vapor quality. At the same time requirements for CCRS efficientoperation would be taken into consideration as well. In addition,generally compressors 104 do not work well with liquids at their inlets.

In a TMS, expansion valve 114 is generally configured to control thevapor quality of the refrigerant fluid emerging from evaporator 116. Asan example, when expansion valve 114 is implemented as an expansionvalve, the expansion valve regulates the mass flow rate of therefrigerant fluid through the valve. In turn, for a given set ofoperating conditions (e.g., ambient temperature, initial pressure in thereceiver, temperature set point value for heat load 118, the vaporquality determines mass flow rate of the refrigerant fluid emerging fromevaporator 116.

Expansion valve 114 typically controls the vapor quality of therefrigerant fluid emerging from evaporator 116 in response toinformation about at least one thermodynamic quantity that is eitherdirectly or indirectly related to the vapor quality.

In general, a wide variety of different measurement and controlstrategies can be implemented in a TMS to achieve the control objectivesdiscussed above. These strategies are presented below. Generally,expansion valve 114 is connected to a measurement device or sensor. Themeasurement device provides information about the thermodynamicquantities upon which adjustments of the control devices are based. Themeasurement devices can be implemented in many different ways, dependingupon the nature of the control devices.

A variety of different refrigerant fluids can be used in a TMS.Depending on application for both open-circuit refrigeration systemoperation and closed-circuit refrigeration system operation, emissionsregulations and operating environments may limit the types ofrefrigerant fluids that can be used.

For example, in certain embodiments, the refrigerant fluid can beammonia having very large latent heat; after passing through the coolingcircuit, ammonia refrigerant vapor in the open-circuit operation can bedisposed of by incineration, by chemical treatment (i.e.,neutralization), and/or by direct venting to atmosphere. In certainembodiments, the refrigerant fluid can be an ammonia-based mixture thatincludes ammonia and one or more other substances. For example, mixturescan include one or more additives that facilitate ammonia absorption orammonia burning.

More generally, any fluid can be used as a refrigerant in theopen-circuit refrigeration systems disclosed herein, provided that thefluid is suitable for cooling heat loads 118, 120 (e.g., the fluid boilsat an appropriate temperature) and, in embodiments where the refrigerantfluid is exhausted directly to the environment, regulations and othersafety and operating considerations do not inhibit such discharge.

One example of refrigerant is ammonia. Ammonia under standard conditionsof pressure and temperature is in a liquid or two-phase state. Thus, thereceiver 110 typically will store ammonia at a saturated pressurecorresponding to the surrounding temperature. The pressure in thereceiver 110 storing ammonia will change during operation. The use ofthe expansion valve 114 can stabilize pressure in the receiver 110during operation, by adjusting the expansion valve 114 (e.g.,automatically or by control system 999) based on a measurement of theevaporation pressure (p_(e)) of the refrigerant fluid and/or ameasurement of the evaporation temperature of the refrigerant fluid.

Control system 999 can adjust expansion valve 114 based on measurementsof one or more of the following system parameter values: the pressuredrop (p_(r)-p_(e)) across expansion valve 114, the pressure drop acrossevaporator 116, the refrigerant fluid pressure in receiver 110 (p _(r)),the vapor quality of the refrigerant fluid emerging from evaporator 116(or at another location in the system), the superheat value of therefrigerant fluid in the system, the evaporation pressure (p_(e)) of therefrigerant fluid, and the evaporation temperature of the refrigerantfluid. To adjust expansion valve 114 based on a particular value of ameasured system parameter value, control system 999 compares themeasured value to a set point value (or threshold value) for the systemparameter, as will be discussed below.

A variety of different refrigerant fluids can be used in any of the OCRSconfigurations. For open-circuit refrigeration systems in general,emissions regulations and operating environments may limit the types ofrefrigerant fluids that can be used. For example, in certainembodiments, the refrigerant fluid can be ammonia having very largelatent heat; after passing through the cooling circuit, vaporizedammonia that is captured at the vapor port of the liquid separator canbe disposed of by incineration, by chemical treatment (i.e.,neutralization), and/or by direct venting to atmosphere. Any liquidcaptured in the liquid separator is recycled back into the OCRSP (eitherdirectly or indirectly).

Since liquid refrigerant temperature is sensitive to ambienttemperature, the density of liquid refrigerant changes even though thepressure in the receiver 110 remains the same. Also, the liquidrefrigerant temperature impacts the vapor quality at the evaporatorinlet. Therefore, the refrigerant mass and volume flow rates change andthe control devices can be used.

Various combinations of the sensors can be used to measure thermodynamicproperties of a TMS that are used to adjust the control devices or pumpsdiscussed above and which signals are processed by the control system999. Connections (wired or wireless) are provided between each of thesensors and control system 999. In many embodiments, system includesonly certain combinations of the sensors (e.g., one, two, three, or fourof the sensors) to provide suitable control signals for the controldevices.

FIG. 7 shows the control system 999 that includes a processor 702,memory 704, storage 706, and I/O interfaces 708, all of which areconnected/coupled together via a bus 710. Any two of the optionaldevices, as pressure sensors, upstream and downstream from a controldevice, can be configured to measure information about a pressuredifferential p_(r)-p_(e) across the respective control device and totransmit electronic signals corresponding to the measured pressure fromwhich a pressure difference information can be generated by the controlsystem 999. Other sensors such as flow sensors and temperature sensorscan be used as well. In certain embodiments, sensors can be replaced bya single pressure differential sensor, a first end of which is connectedadjacent to an inlet and a second end of which is connected adjacent toan outlet of a device to which differential pressure is to be measured,such as the evaporator. The pressure differential sensor measures andtransmits information about the refrigerant fluid pressure drop acrossthe device, e.g., the evaporator 116.

Temperature sensors can be positioned adjacent to an inlet or an outletof e.g., the evaporator 116 or between the inlet and the outlet. Such atemperature sensor measures temperature information for the refrigerantfluid within evaporator 116 (which represents the evaporatingtemperature) and transmits an electronic signal corresponding to themeasured information. A temperature sensor can be attached to heat loads118 and/or heat loads 120, which measures temperature information forthe load and transmits an electronic signal corresponding to themeasured information. An optional temperature sensor can be adjacent tothe outlet of evaporator 116 that measures and transmits informationabout the temperature of the refrigerant fluid as it emerges fromevaporator 116.

In certain embodiments, the systems disclosed herein are configured todetermine superheat information for the refrigerant fluid based ontemperature and pressure information for the refrigerant fluid measuredby any of the sensors disclosed herein. The superheat of the refrigerantvapor refers to the difference between the temperature of therefrigerant fluid vapor at a measurement point in a TMS and thesaturated vapor temperature of the refrigerant fluid defined by therefrigerant pressure at the measurement point in a TMS.

To determine the superheat associated with the refrigerant fluid, thesystem control system 999 (as described) receives information about therefrigerant fluid vapor pressure after emerging from a heat exchangerdownstream from evaporator 116, and uses calibration information, alookup table, a mathematical relationship, or other information todetermine the saturated vapor temperature for the refrigerant fluid fromthe pressure information. The control system 999 also receivesinformation about actual temperature of the refrigerant fluid, and thencalculates the superheat associated with the refrigerant fluid as thedifference between actual temperature of the refrigerant fluid and thesaturated vapor temperature for the refrigerant fluid.

The foregoing temperature sensors can be implemented in a variety ofways in a TMS. As one example, thermocouples and thermistors canfunction as temperature sensors in a TMS. Examples of suitablecommercially available temperature sensors for use in a TMS include, butare not limited to, the 88000 series thermocouple surface probes(available from OMEGA Engineering Inc., Norwalk, Conn.).

A TMS can include a vapor quality sensor that measures vapor quality ofthe refrigerant fluid emerging from evaporator 116. Typically, such asensor is implemented as a capacitive sensor that measures a differencein capacitance between the liquid and vapor phases of the refrigerantfluid. The capacitance information can be used to directly determine thevapor quality of the refrigerant fluid (e.g., by system control system999). Alternatively, sensor can determine the vapor quality directlybased on the differential capacitance measurements and transmit anelectronic signal that includes information about the refrigerant fluidvapor quality. Examples of commercially available vapor quality sensorsthat can be used in a TMS include, but are not limited to, HBX sensors(available from HB Products, Hasselager, Denmark).

It should generally understood that the systems disclosed herein caninclude a variety of combinations of the various sensors describedabove, and control system 999 can receive measurement informationperiodically or aperiodically from any of the various sensors. Moreover,it should be understood any of the sensors described can operateautonomously, measuring information and transmitting the information tocontrol system 999 (or directly to the first and/or second controldevice) or, alternatively, any of the sensors described above canmeasure information when activated by control system 999 via a suitablecontrol signal, and measure and transmit information to control system999 in response to activating control signal.

To adjust a control device on a particular value of a measured systemparameter value, control system 999 compares the measured value to a setpoint value (or threshold value) for the system parameter. Certain setpoint values represent a maximum allowable value of a system parameter,and if the measured value is equal to the set point value (or differsfrom the set point value by 10% or less (e.g., 5% or less, 3% or less,1% or less) of the set point value), control system 999 adjusts arespective control device to modify the operating state of a TMS.Certain set point values represent a minimum allowable value of a systemparameter, and if the measured value is equal to the set point value (ordiffers from the set point value by 10% or less (e.g., 5% or less, 3% orless, 1% or less) of the set point value), control system 999 adjuststhe respective control device to modify the operating state of a TMS,and increase the system parameter value. The control system 999 executesalgorithms that use the measured sensor value(s) to provide signals thatcause the various control devices to adjust refrigerant flow rates, etc.

Some set point values represent “target” values of system parameters.For such system parameters, if the measured parameter value differs fromthe set point value by 1% or more (e.g., 3% or more, 5% or more, 10% ormore, 20% or more), control system 999 adjusts the respective controldevice to adjust the operating state of the system, so that the systemparameter value more closely matches the set point value.

Optional pressure sensors are configured to measure information aboutthe pressure differential p_(r)-p_(e) across a control device and totransmit an electronic signal corresponding to the measured pressuredifference information. Two sensors can effectively measure p_(r),p_(e). In certain embodiments two sensors can be replaced by a singlepressure differential sensor. Where a pressure differential sensor isused, a first end of the sensor is connected upstream of a first controldevice and a second end of the sensor is connected downstream from firstcontrol device.

System also includes optional pressure sensors positioned at the inletand outlet, respectively, of evaporator 116. A sensor measures andtransmits information about the refrigerant fluid pressure upstream fromevaporator 116, and a sensor measure and transmit information about therefrigerant fluid pressure downstream from evaporator 116. Thisinformation can be used (e.g., by a system controller) to calculate therefrigerant fluid pressure drop across evaporator 116. As above, incertain embodiments, sensors can be replaced by a single pressuredifferential sensor to measure and transmit the refrigerant fluidpressure drop across evaporator 116.

To measure the evaporating pressure (p_(e)) a sensor can be optionallypositioned between the inlet and outlet of evaporator 116, i.e.,internal to evaporator 116. In such a configuration, the sensor canprovide a direct a direct measurement of the evaporating pressure.

To measure refrigerant fluid pressure at other locations within system,sensor can also optionally be positioned, for example, in-line along aconduit. Pressure sensors at each of these locations can be used toprovide information about the refrigerant fluid pressure downstream fromevaporator 116, or the pressure drop across evaporator 116.

It should be appreciated that, in the foregoing discussion, any one orvarious combinations of two sensors discussed in connection with systemcan correspond to the first measurement device connected to expansionvalve 114, and any one or various combination of two sensors cancorrespond to the second measurement device. In general, as discussedpreviously, the first measurement device provides informationcorresponding to a first thermodynamic quantity to the first controldevice, and the second measurement device provides informationcorresponding to a second thermodynamic quantity to the second controldevice, where the first and second thermodynamic quantities aredifferent, and therefore allow the first and second control device toindependently control two different system properties (e.g., the vaporquality of the refrigerant fluid and the heat load temperature,respectively).

In some embodiments, one or more of the sensors shown in system areconnected directly to expansion valve 114. The first and second controldevices (expansion valve 114 and flow control valve 530 for example),for example, can be configured to adaptively respond directly to thetransmitted signals from the sensors, thereby providing for automaticadjustment of the system's operating parameters. In certain embodiments,the first and/or second control device can include processing hardwareand/or software components that receive transmitted signals from thesensors, optionally perform computational operations, and activateelements of the first and/or second control device to adjust the controldevice in response to the sensor signals.

In addition, control system 999 is optionally connected to expansionvalve 114. In embodiments where expansion valve 114 is implemented as adevice controllable via an electrical control signal, control system 999is configured to transmit suitable control signals to the first and/orsecond control device to adjust the configuration of these components.In particular, control system 999 is configured to adjust expansionvalve 114 to control the vapor quality of the refrigerant fluid in aTMS.

During operation of the a TMS, control system 999 typically receivesmeasurement signals from one or more sensors. The measurements can bereceived periodically (e.g., at consistent, recurring intervals) orirregularly, depending upon the nature of the measurements and themanner in which the measurement information is used by control system999. In some embodiments, certain measurements are performed by controlsystem 999 after particular conditions—such as a measured parametervalue exceeding or falling below an associated set point value—arereached.

By way of example, Table 1 summarizes various examples of combinationsof types of information (e.g., system properties and thermodynamicquantities) that can be measured by the sensors of system andtransmitted to control system 999, to allow control system 999 togenerate and transmit suitable control signals to expansion valve 114and/or other control devices. The types of information shown in Table 1can generally be measured using any suitable device (includingcombination of one or more of the sensors discussed herein) to providemeasurement information to control system 999.

TABLE 1 Measurement Information Used to Adjust Control Device FCM EvapPress Press Rec Evap Evap HL Drop Drop Pres VQ SH VQ P/T TempMeasurement FCM Press Drop x x Information Evap Press Drop x x Used toRec Press x x Adjust VQ x x Control SH x x Device Evap VQ x x Evap P/T xx x x x x x HL Temp x x x x x x x

FCM Press Drop=refrigerant fluid pressure drop across first controldevice

Evap Press Drop=refrigerant fluid pressure drop across evaporator

Rec Press=refrigerant fluid pressure in receiver

VQ=vapor quality of refrigerant fluid

SH=superheat of refrigerant fluid

Evap VQ=vapor quality of refrigerant fluid at evaporator outlet

Evap P/T=evaporation pressure or temperature

HL Temp=heat load temperature

For example, in some embodiments, expansion valve 114 is adjusted (e.g.,automatically or by control system 999) based on a measurement of theevaporation pressure (p_(e)) of the refrigerant fluid and/or ameasurement of the evaporation temperature of the refrigerant fluid. Incertain embodiments, expansion valve 114 is adjusted (e.g.,automatically or by control system 999) based on a measurement of thetemperature of thermal load 49 b.

To adjust any of the control devices, the compressor 104, or the pump602 based on a particular value of a measured system parameter value,control system 999 compares the measured value to a set point value (orthreshold value) for the system parameter. Certain set point valuesrepresent a maximum allowable value of a system parameter, and if themeasured value is equal to the set point value (or differs from the setpoint value by 10% or less (e.g., 5% or less, 3% or less, 1% or less) ofthe set point value), control system 999 adjusts expansion valve 114 toadjust the operating state of the system, and reduce the systemparameter value.

Certain set point values represent a minimum allowable value of a systemparameter, and if the measured value is equal to the set point value (ordiffers from the set point value by 10% or less (e.g., 5% or less, 3% orless, 1% or less) of the set point value), control system 999 adjustsexpansion valve 114, etc. to adjust the operating state of the system,and increase the system parameter value.

Some set point values represent “target” values of system parameters.For such system parameters, if the measured parameter value differs fromthe set point value by 1% or more (e.g., 3% or more, 5% or more, 10% ormore, 20% or more), control system 999 adjusts expansion valve 114, etc.to adjust the operating state of the system, so that the systemparameter value more closely matches the set point value.

Measured parameter values are assessed in relative terms based on setpoint values (i.e., as a percentage of set point values). Alternatively,in some embodiments, measured parameter values can be accessed inabsolute terms. For example, if a measured system parameter valuediffers from a set point value by more than a certain amount (e.g., by 1degree C. or more, 2 degrees C. or more, 3 degrees C. or more, 4 degreesC. or more, 5 degrees C. or more), then control system 999 adjustsexpansion valve 114, etc. to adjust the operating state of the system,so that the measured system parameter value more closely matches the setpoint value.

In the foregoing examples, measured parameter values are assessed inrelative terms based on set point values (i.e., as a percentage of setpoint values). Alternatively, in some embodiments, measured parametervalues can be in absolute terms. For example, if a measured systemparameter value differs from a set point value by more than a certainamount (e.g., by 1 degree C. or more, 2 degrees C. or more, 3 degrees C.or more, 4 degrees C. or more, 5 degrees C. or more), then controlsystem 999 adjusts expansion valve 114, etc. to adjust the operatingstate of the system, so that the measured system parameter value moreclosely matches the set point value.

In certain embodiments, refrigerant fluid emerging from evaporator 116can be used to cool one or more additional thermal loads. In addition,systems can include a second thermal load connected to a heat exchanger.A variety of mechanical connections can be used to attach second thermalload to heat exchanger, including (but not limited to) brazing,clamping, welding, and any of the other connection types discussedherein.

Heat exchangers include one or more flow channels through which highvapor quality refrigerant fluid flows after leaving evaporator 116.During operation, as the refrigerant fluid vapor phases through the flowchannels, it absorbs heat energy from second thermal load, coolingsecond thermal load. Typically, second thermal load is not as sensitiveas thermal load 118 to fluctuations in temperature. Accordingly, whilesecond thermal load is generally not cooled as precisely relative to aparticular temperature set point value as thermal loads 120, therefrigerant fluid vapor provides cooling that adequately matches thetemperature constraints for second thermal load.

In general, the TMS disclosed herein can include more than one (e.g.,two or more, three or more, four or more, five or more, or even more)thermal loads in addition to thermal loads depicted. Each of additionalthermal loads can have an associated heat exchanger; in someembodiments, multiple additional thermal loads are connected to a singleheat exchanger, and in certain embodiments, each additional thermal loadhas its own heat exchanger. Moreover, each of additional thermal loadscan be cooled by the superheated refrigerant fluid vapor after a heatexchanger attached to the second load or cooled by the high vaporquality fluid stream that emerges from evaporator 116.

Although evaporator 116 and heat exchanger are implemented as separatecomponents, in certain embodiments, these components can be integratedto form a single heat exchanger, with thermal load and second thermalload both connected to the single heat exchanger. The refrigerant fluidvapor that is discharged from the evaporator portion of the single heatexchanger is used to cool second thermal load, which is connected to asecond portion of the single heat exchanger.

The vapor quality of the refrigerant fluid after passing throughevaporator 116 can be controlled either directly or indirectly withrespect to a vapor quality set point by control system 999. In someembodiments, the system includes a vapor quality sensor that provides adirect measurement of vapor quality, which is transmitted to controlsystem 999. Control system 999 adjusts control device depending onconfiguration to control the vapor quality relative to the vapor qualityset point value.

In certain embodiments, the system includes a sensor that measuressuperheat and indirectly, vapor quality. For example, a combination oftemperature and pressure sensors measure the refrigerant fluid superheatdownstream from a second heat load, and transmit the measurements tocontrol system 999. Control system 999 adjusts control device accordingto the configuration based on the measured superheat relative to asuperheat set point value. By doing so, control system 999 indirectlyadjusts the vapor quality of the refrigerant fluid emerging fromevaporator 116.

As the two refrigerant fluid streams flow in opposite directions withinrecuperative heat exchanger, heat is transferred from the refrigerantfluid emerging from evaporator 116 to the refrigerant fluid enteringexpansion valve 114. Heat transfer between the refrigerant fluid streamscan have a number of advantages. For example, recuperative heat transfercan increase the refrigeration effect in evaporator 116, reducing therefrigerant mass transfer rate implemented to handle the heat loadpresented by high heat load 118. Further, by reducing the refrigerantmass transfer rate through evaporator 116, amount of refrigerant used toprovide cooling duty in a given period of time is reduced. As a result,for a given initial quantity of refrigerant fluid introduced intoreceiver 110, the operational time over which the system can operatebefore an additional refrigerant fluid charge is needed can be extended.Alternatively, for the system to effectively cool high heat load 118 fora given period of time, a smaller initial charge of refrigerant fluidinto receiver 110 can be used.

Because the liquid and vapor phases of the two-phase mixture ofrefrigerant fluid generated following expansion of the refrigerant fluidin expansion valve 114 can be used for different cooling applications,in some embodiments, the system can include a phase separator toseparate the liquid and vapor phases into separate refrigerant streamsthat follow different flow paths within a TMS.

Further, eliminating (or nearly eliminating) the refrigerant vapor fromthe refrigerant fluid stream entering evaporator 116 can help to reducethe cross-section of the evaporator and improve film boiling in therefrigerant channels. In film boiling, the liquid phase (in the form ofa film) is physically separated from the walls of the refrigerantchannels by a layer of refrigerant vapor, leading to poor thermalcontact and heat transfer between the refrigerant liquid and therefrigerant channels. Reducing film boiling improves the efficiency ofheat transfer and the cooling performance of evaporator 116.

In addition, by eliminating (or nearly eliminating) the refrigerantvapor from the refrigerant fluid stream entering evaporator 116,distribution of the liquid refrigerant within the channels of evaporator116 can be made easier. In certain embodiments, vapor present in therefrigerant channels of evaporator 116 can oppose the flow of liquidrefrigerant into the channels. Diverting the vapor phase of therefrigerant fluid before the fluid enters evaporator 116 can help toreduce this difficulty.

In addition to phase separator, or as an alternative to phase separator,in some embodiments the systems disclosed herein can include a phaseseparator downstream from evaporator 116. Such a configuration can beused when the refrigerant fluid emerging from evaporator is not entirelyin the vapor phase, and still includes liquid refrigerant fluid.

The foregoing examples of thermal management systems illustrate a numberof features that can be included in any of the systems within the scopeof this disclosure. In addition, a variety of other features can bepresent in such systems.

In certain embodiments, refrigerant fluid that is discharged fromevaporator 116 and passes through conduit can be directly discharged asexhaust from conduit without further treatment. Direct dischargeprovides a convenient and straightforward method for handling spentrefrigerant, and has added advantage that over time, the overall weightof the system is reduced due to the loss of refrigerant fluid. Forsystems that are mounted to small vehicles or are otherwise mobile, thisreduction in weight can be important.

In some embodiments, however, refrigerant fluid vapor can be furtherprocessed before it is discharged. Further processing may be desirabledepending upon the nature of the refrigerant fluid that is used, asdirect discharge of unprocessed refrigerant fluid vapor may be hazardousto humans and/or may be deleterious to mechanical and/or electronicdevices in the vicinity of a TMS. For example, the unprocessedrefrigerant fluid vapor may be flammable or toxic, or may corrodemetallic device components. In situations such as these, additionalprocessing of the refrigerant fluid vapor may be desirable.

In general, refrigerant processing apparatus can be implemented invarious ways. In some embodiments, refrigerant processing apparatus is achemical scrubber or water-based scrubber. Within apparatus, therefrigerant fluid is exposed to one or more chemical agents that treatthe refrigerant fluid vapor to reduce its deleterious properties. Forexample, where the refrigerant fluid vapor is basic (e.g., ammonia) oracidic, the refrigerant fluid vapor can be exposed to one or morechemical agents that neutralize the vapor and yield a less basic oracidic product that can be collected for disposal or discharged fromapparatus.

As another example, where the refrigerant fluid vapor is highlychemically reactive, the refrigerant fluid vapor can be exposed to oneor more chemical agents that oxidize, reduce, or otherwise react withthe refrigerant fluid vapor to yield a less reactive product that can becollected for disposal or discharged from apparatus.

In certain embodiments, refrigerant processing apparatus can beimplemented as an adsorptive sink for the refrigerant fluid. Apparatuscan include, for example, an adsorbent material bed that binds particlesof the refrigerant fluid vapor, trapping the refrigerant fluid withinapparatus and preventing discharge. The adsorptive process can sequesterthe refrigerant fluid particles within adsorbent material bed, which canthen be removed from apparatus and sent for disposal.

In some embodiments, where the refrigerant fluid is flammable,refrigerant processing apparatus can be implemented as an incinerator.Incoming refrigerant fluid vapor can be mixed with oxygen or anotheroxidizing agent and ignited to combust the refrigerant fluid. Thecombustion products can be discharged from the incinerator or collected(e.g., via an adsorbent material bed) for later disposal.

As an alternative, refrigerant processing apparatus can also beimplemented as a combustor of an engine or another mechanicalpower-generating device. Refrigerant fluid vapor from conduit can bemixed with oxygen, for example, and combusted in a piston-based engineor turbine to perform mechanical work, such as providing drive power fora vehicle or driving a generator to produce electricity. In certainembodiments, the generated electricity can be used to provide electricaloperating power for one or more devices, including high heat load 118.For example, high heat load 118 can include one or more electronicdevices that are powered, at least in part, by electrical energygenerated from combustion of refrigerant fluid vapor in refrigerantprocessing apparatus.

The thermal management systems disclosed herein can optionally include aphase separator upstream from the refrigerant processing apparatus.

Particularly during start-up of the systems disclosed herein, liquidrefrigerant may be present in conduits because the systems generallybegin operation before high heat loads 118 and/or low heat loads 120 areactivated. Accordingly, phase separator functions in a manner similar tophase separators to separate liquid refrigerant fluid from refrigerantvapor. The separated liquid refrigerant fluid can be re-directed toanother portion of the system, or retained within phase separator untilit is converted to refrigerant vapor. By using phase separator, liquidrefrigerant fluid can be prevented from entering refrigerant processingapparatus.

In some embodiments, the refrigeration systems disclosed herein can becombined with power systems to form integrated power and thermalsystems, in which certain components of the integrated systems areresponsible for providing refrigeration functions and certain componentsof the integrated systems are responsible for generating operatingpower.

FIG. 8 shows an integrated power and a TMS that includes many featuressimilar to those discussed above with only aspects of an OCRS (e.g.,OCRS 5 or other OCRS described herein) shown. In addition, a TMSincludes, is coupled to, or is part of an engine 800 with an inlet thatreceives the stream of waste refrigerant fluid. Engine 800 can combustthe waste refrigerant fluid directly, or alternatively can mix the wasterefrigerant fluid with one or more additives (such as oxidizers) beforecombustion. Where ammonia is used as the refrigerant fluid in OCRS 5,suitable engine configurations for both direct ammonia combustion asfuel, and combustion of ammonia mixed with other additives, can beimplemented. In general, combustion of ammonia improves the efficiencyof power generation by the engine.

The energy released from combustion of the refrigerant fluid can be usedby engine 800 to generate electrical power, e.g., by using the energy todrive a generator. The electrical power can be delivered via electricalconnection to high heat loads 118 to provide operating power for theload. For example, in certain embodiments, high heat loads 118 includeone or more electrical circuits and/or electronic devices, and engine800 provides operating power to the circuits/devices via combustion ofrefrigerant fluid. Byproducts 802 of the combustion process can bedischarged from engine 800 via exhaust conduit, as shown in FIG. 8 .

Various types of engines and power-generating devices can be implementedas engine 800 in a TMS. In some embodiments, for example, engine 800 isa conventional four-cycle piston-based engine, and the waste refrigerantfluid is introduced into a combustor of the engine. In certainembodiments, engine 800 is a gas turbine engine, and the wasterefrigerant fluid is introduced via the engine inlet to afterburner ofthe gas turbine engine. As discussed above, in some embodiments, a TMScan include phase separator (not shown) positioned upstream from engine140. Phase separator functions to prevent liquid refrigerant fluid fromentering engine 800, which may reduce the efficiency of electrical powergeneration by engine 800.

In certain embodiments, the thermal management systems disclosed hereinoperate differently at, and immediately following, system start-up,compared to the manner in which the systems operate after an extendedrunning period. Upon start-up, the compressor 104 and a device (usuallya fan) moving a cooling fluid (usually ambient air) through thecondenser 106 are powered. The compressor 104 discharges compressedrefrigerant into the condenser 106. The refrigerant is condensed andsubcooled in the condenser 106. Liquid refrigerant fluid enters receiver110 at a pressure and temperature generated by operation of thecompressor 104 and condenser 106.

The thermal management systems and methods disclosed herein can beimplemented as part of (or in conjunction with) directed energy systemssuch as high energy laser systems. Due to their nature, directed energysystems typically present a number of cooling challenges, includingcertain heat loads for which temperatures are maintained duringoperation within a relatively narrow range.

FIG. 9 shows one example of a directed energy system, specifically, ahigh energy laser system 900. System 900 includes a bank of one or morelaser diodes 902 and an amplifier 804 connected to a power source 906.During operation, laser diodes 902 generate an output radiation beam 908that is amplified by amplifier 804, and directed as output beam 910 ontoa target. Generation of high energy output beams can result in theproduction of significant quantities of heat. Certain laser diodes,however, are relatively temperature sensitive, and the operatingtemperature of such diodes is regulated within a relatively narrow rangeof temperatures to ensure efficient operation and avoid thermal damage.Amplifiers are also temperature-sensitively, although typically lesssensitive than diodes.

To regulate the temperatures of various components of directed energysystems such as diodes 902 and amplifier 804, such systems can includecomponents and features of the thermal management systems disclosedherein. In FIG. 19 , a portion of evaporator 116 (FIGS. 1, 2 , etc.) iscoupled to diodes 902, while another portion 24′ of the evaporator 116is coupled to amplifier 804. The other components of the thermalmanagement systems disclosed herein are not shown for clarity. However,it should be understood that any of the features and componentsdiscussed above can optionally be included in directed energy systems.Diodes 902, due to their temperature-sensitive nature, effectivelyfunction as a high heat loads 118 in system 900, while amplifier 804functions as a low heat loads 120.

System 900 is one example of a directed energy system that can includevarious features and components of the thermal management systems andmethods described herein. However, it should be appreciated that thethermal management systems and methods are general in nature, and can beapplied to cool a variety of different heat loads under a wide range ofoperating conditions.

Control system 999 can generally be implemented as any one of a varietyof different electrical or electronic computing or processing devices,and can perform any combination of the various steps discussed above tocontrol various components of the disclosed thermal management systems.

Control system 999 can generally, and optionally, include any one ormore of a processor (or multiple processors), a memory, a storagedevice, and input/output device. Some or all of these components can beinterconnected using a system bus. The processor is capable ofprocessing instructions for execution. In some embodiments, theprocessor is a single-threaded processor. In certain embodiments, theprocessor is a multi-threaded processor. Typically, the processor iscapable of processing instructions stored in the memory or on thestorage device to display graphical information for a user interface onthe input/output device, and to execute the various monitoring andcontrol functions discussed above. Suitable processors for the systemsdisclosed herein include both general and special purposemicroprocessors, and the sole processor or one of multiple processors ofany kind of computer or computing device.

The memory stores information within the system, and can be acomputer-readable medium, such as a volatile or non-volatile memory. Thestorage device can be capable of providing mass storage for the controlsystem 999. In general, the storage device can include anynon-transitory tangible media configured to store computer readableinstructions. For example, the storage device can include acomputer-readable medium and associated components, including: magneticdisks, such as internal hard disks and removable disks; magneto-opticaldisks; and optical disks. Storage devices suitable for tangiblyembodying computer program instructions and data include all forms ofnon-volatile memory including by way of example, semiconductor memorydevices, such as

EPROM, EEPROM, and flash memory devices; magnetic disks such as internalhard disks and removable disks; magneto-optical disks; and CD-ROM andDVD-ROM disks. Processors and memory units of the systems disclosedherein can be supplemented by, or incorporated in, ASICs(application-specific integrated circuits).

The input/output device provides input/output operations for controlsystem 999, and can include a keyboard and/or pointing device. In someembodiments, the input/output device includes a display unit fordisplaying graphical user interfaces and system related information.

The features described herein, including components for performingvarious measurement, monitoring, control, and communication functions,can be implemented in digital electronic circuitry, or in computerhardware, firmware, or in combinations of them. Methods steps can beimplemented in a computer program product tangibly embodied in aninformation carrier, e.g., in a machine-readable storage device, forexecution by a programmable processor (e.g., of control system 999), andfeatures can be performed by a programmable processor executing such aprogram of instructions to perform any of the steps and functionsdescribed above. Computer programs suitable for execution by one or moresystem processors include a set of instructions that can be useddirectly or indirectly, to cause a processor or other computing deviceexecuting the instructions to perform certain activities, including thevarious steps discussed above.

Computer programs suitable for use with the systems and methodsdisclosed herein can be written in any form of programming language,including compiled or interpreted languages, and can be deployed in anyform, including as stand-alone programs or as modules, components,subroutines, or other units suitable for use in a computing environment.

In addition to one or more processors and/or computing componentsimplemented as part of control system 999, the systems disclosed hereincan include additional processors and/or computing components within anyof the control device (e.g., expansion valve 114) and any of the sensorsdiscussed above. Processors and/or computing components of the controldevices and sensors, and software programs and instructions that areexecuted by such processors and/or computing components, can generallyhave any of the features discussed above in connection with controlsystem 999.

A number of embodiments have been described. Nevertheless, it will beunderstood that various modifications may be made without departing fromthe spirit and scope of the disclosure. Accordingly, other embodimentsare within the scope of the following claims.

What is claimed is:
 1. A heat transfer apparatus, comprising: aplurality of “n” number of control valves, each of the plurality of “n”number of control valves comprising a control valve inlet and a controlvalve outlet; a like plurality of “n” number of evaporator sections,each of the like plurality of “n” number of evaporator sectionscomprising an evaporator section inlet and an evaporator section outlet,each evaporator section inlet fluidly coupled to a corresponding one ofthe plurality of “n” number of control valve outlets, each evaporatorsection configured to extract heat from at least one heat load that isin thermal conductive or convective contact or proximate to theevaporator section; a refrigerant fluid inlet fluidly coupled to thelike plurality of evaporator sections; and a refrigerant fluid outletfluidly coupled to the like plurality of evaporator sections.
 2. Theheat transfer apparatus of claim 1, wherein the plurality of “n” numberof control valves are fluidly coupled between the refrigerant fluidinlet and the evaporator outlets.
 3. The heat transfer apparatus ofclaim 1, wherein each of the plurality of “n” number of control valvesis configured to receive a control signal.
 4. The heat transferapparatus of claim 1, wherein the refrigerant fluid inlet comprises aninlet distributor having a plurality of outlets, with each of theplurality of outlets being coupled to the inlet of a corresponding oneof the plurality of “n” number of control valves, and the refrigerantfluid outlet comprises an outlet collector having a plurality of inlets,with each of the plurality of inlets being coupled to the evaporatorsection outlet of a corresponding one of the like plurality ofevaporator sections.
 5. The heat transfer apparatus of claim 1, whereinthe plurality of “n” number of control valves are configured toselectively: expand a refrigerant fluid to generate a refrigerant fluidmixture comprising liquid refrigerant fluid and refrigerant fluid vapor;and direct the refrigerant fluid mixture into the corresponding likeplurality of evaporator sections.
 6. The heat transfer apparatus ofclaim 5, wherein the plurality of “n” number of control valves compriseexpansion valves that are further configured to selectively stop arefrigerant fluid flow through the expansion valves.
 7. A method ofcooling at least one heat load, comprising: providing a flow of arefrigerant fluid to a refrigerant fluid inlet of a heat transferdevice; providing the flow of the refrigerant fluid from the refrigerantfluid inlet to a plurality of “n” number of control valves, each of theplurality of “n” number of control valves comprising a control valveinlet and a control valve outlet; providing the flow of the refrigerantfluid from the refrigerant fluid inlet to a like plurality of “n” numberof evaporator sections, each of the like plurality of “n” number ofevaporator sections comprising an evaporator section inlet and anevaporator section outlet, each evaporator section inlet fluidly coupledto a corresponding one of the plurality of “n” number of control valveoutlets; extracting heat, with at least one evaporator section, from atleast one heat load that is in thermal conductive or convective contactor proximate to the evaporator section; and providing the flow of therefrigerant fluid through a refrigerant fluid outlet fluidly coupled tothe like plurality of evaporator sections.
 8. The method of claim 7,further comprising: expanding, in at least one of the a plurality of “n”number of control valves, the refrigerant fluid to generate arefrigerant fluid mixture comprising liquid refrigerant fluid andrefrigerant fluid vapor; and directing the refrigerant fluid mixtureinto the corresponding at least one evaporator section.
 9. The method ofclaim 8, further comprising selectively stopping the flow of therefrigerant fluid through the heat transfer device with the controlvalves.
 10. The method of claim 7, further comprising: directing therefrigerant fluid to enter a first set of “n”- “x” number of theplurality of evaporator sections over a first interval, while inhibitingthe refrigerant fluid to enter a second, different set of “x” number ofthe plurality of evaporator sections over the first interval, where “n”is a total number of the plurality of evaporator sections; and switchingthe refrigerant fluid to direct the transported refrigerant fluid thatenters the gated evaporator to contact a third, different set of “n”-“x”′ number of the plurality of evaporator sections over a second,subsequent interval, while inhibiting the refrigerant fluid to enter afourth, different set of “x”′ number of the plurality of evaporatorsections over the second interval.
 11. A thermal management system,comprising: an open-circuit refrigeration system (OCRS), comprising: areceiver configured to store a refrigerant fluid; at least one gatedevaporator configured to extract heat from a plurality of heat loadswhen the plurality of heat loads are in thermal conductive or convectivecontact or proximate to the gated evaporator, with the gated evaporatorcomprising: a plurality of “n” number of control valves, each of theplurality of “n” number of control valves having a control valve inletand a control valve outlet; and a like plurality of evaporator sections,each of the like plurality of evaporator sections having an evaporatorsection inlet and an evaporator section outlet, with each evaporatorsection inlet coupled to a corresponding one of the plurality of “n”number of control valve outlets; an exhaust line; and a flow controldevice having an inlet and having an outlet, with the outlet coupled toan exhaust line, the flow control device configured to control arefrigerant fluid pressure upstream of the flow control device, with thereceiver, the gated evaporator, the flow control device, and the exhaustline fluidly coupled to form an open-circuit refrigerant fluid flowpath.
 12. The system of claim 11, further comprising an inletdistributor coupled to the outlet of the receiver, and having aplurality of outlets, with each of the plurality of outlets beingcoupled to the inlet of a corresponding one of the plurality of “n”number of control valves.
 13. The system of claim 11, further comprisingan outlet collector having a plurality of inlets with each of theplurality of inlets being coupled to the evaporator section outlet of acorresponding one of the like plurality of evaporator sections, andhaving an outlet coupled to the inlet of the flow control device. 14.The system of claim 11, wherein the plurality of “n” number of controlvalves are configured to selectively: expand the refrigerant fluid togenerate a refrigerant fluid mixture comprising liquid refrigerant fluidand refrigerant fluid vapor; and direct the refrigerant fluid mixtureinto the corresponding like plurality of evaporator sections.
 15. Thesystem of claim 14, wherein the plurality of “n” number of controlvalves are expansion valves that are further configured to selectivelystop refrigerant fluid flow through the expansion valves.
 16. The systemof claim 11, wherein the plurality of “n” number of control valves areexpansion valves that are not configured to stop refrigerant fluid flowthrough the expansion valves, with the system further comprising aplurality of solenoid control valves coupled to the expansion valves,the plurality of solenoid valves configured to selectively stop therefrigerant fluid flow through the expansion valves.
 17. The system ofclaim 11, wherein the plurality of “n” number of control valves areconfigured to selectively perform a constant-enthalpy expansion of aliquid refrigerant fluid to generate a refrigerant fluid mixture for thelike plurality of evaporator sections.
 18. The system of claim 11,wherein the refrigerant fluid comprises ammonia.
 19. The system of claim11, wherein the plurality of “n” number of control valves are furtherconfigured to control temperatures of the plurality of heat loads. 20.The system of claim 11, wherein the flow control device comprises aback-pressure regulator connected downstream from the evaporator alongthe open-circuit refrigerant fluid flow path.
 21. The system of claim20, wherein the back-pressure regulator is configurable to receiverefrigerant fluid vapor generated in the gated evaporator and toregulate the pressure of the refrigerant fluid upstream from theback-pressure regulator along the refrigerant fluid flow path.
 22. Thesystem of claim 20, wherein the back-pressure regulator is configurableto discharge the refrigerant vapor through the exhaust line, withoutreturning the refrigerant vapor to the receiver.
 23. The system of claim11, wherein the refrigerant fluid from the exhaust line is discharged sothat the discharged refrigerant fluid is not returned to the receiver.24. The system of claim 11, further comprising a control systemconfigured to respond to signals from at least one sensor to controloperation of the plurality of “n” number of control valves.
 25. Thesystem of claim 24, wherein the control system is configured to processthe signals from the at least one sensor to switch “x” number of theplurality of “n” number of control valves to inhibit refrigerant flowthrough the “x” number of the plurality of “n” number of control valvesduring a period, with “x” having a value that is at least one less than“n”.”
 26. The system of claim 24, wherein the control system isconfigured to process signals that are time period signals to indicatethat “x” number of uncooled evaporator sections have reached a maximumtime period for a heat load operation, with “x” having a value that isat least one less than “n.”
 27. The system of claim 24, wherein thecontrol system is configured to process signals that are temperaturesignals to indicate that “x” number of the uncooled evaporator sectionshave reached the maximum heat load temperature rise during a heat loadoperation, with “x” having a value that is at least one less than “n.”28. The system of claim 24, wherein the control system is configured toprocess signals that are temperature signals to indicate that “x” numberof uncooled evaporator sections have reached a maximum evaporatorsection temperature rise during a heat load operation, with “x” having avalue that is at least one less than “n.”
 29. The system of claim 21,wherein the flow control device is a first flow control device, and thesystem further comprises a second flow control device coupled betweenthe receiver outlet and the inlet to the flow distributer, with thesecond flow control device configured to control vapor quality at theoutlet of the gated evaporator.
 30. The system of claim 21, furthercomprising a closed-circuit refrigeration system (CCRS) integrated withthe OCRS.
 31. The system of claim 30, further comprising a liquidseparator having an inlet, a vapor-side outlet, and a liquid-sideoutlet.
 32. The system of claim 31, wherein the CCRS comprises: acompressor having a compressor inlet fluidly coupled to the vapor-sideoutlet and having a compressor outlet; and a condenser having acondenser inlet fluidly coupled to the compressor outlet and having acondenser outlet coupled to an inlet of the receiver to condense asuperheated refrigerant vapor at the condenser inlet by removing heatfrom the refrigerant fluid.
 33. The system of claim 32, furthercomprising a junction having an inlet fluidly coupled to the vapor-sideoutlet of the liquid separator and first and second outlets fluidlycoupled to the compressor inlet and the inlet of the flow controldevice.
 34. The system of claim 31, further comprising: anelectronically controllable expansion valve; a sensor disposeddownstream of the gated evaporator to generate a sensor signal thatdirectly or indirectly controls the electronically controllableexpansion valve.
 35. The system of claim 31, further comprising arecuperative heat exchanger that has a first fluid path that receivesthe refrigerant fluid from the receiver and a second fluid path thatreceives refrigerant vapor from the vapor-side outlet, with the secondfluid path providing thermal contact between the refrigerant fluidleaving the receiver and the refrigerant vapor passing through therecuperative heat exchanger.
 36. The system of claim 35, wherein therecuperative heat exchanger evaporates any remaining liquid prior tobeing fed to the inlet of the compressor.
 37. The system of claim 35,further comprising: an electronically controllable expansion valve; asensor disposed downstream of the gated evaporator to generate a sensorsignal that directly or indirectly controls the electronicallycontrollable expansion valve, with the electronically controlledexpansion valve operated with the sensor to maintain a superheat at anoutlet of the recuperative heat exchanger.
 38. The system of claim 37,wherein the recuperative heat exchanger is configured to transfer heatenergy from the refrigerant fluid emerging from liquid separator torefrigerant fluid upstream from the electronically controllableexpansion valve.
 39. The system of claim 31, further comprising anejector having a primary inlet, a secondary inlet, and an outlet, withthe primary inlet fluidly coupled to receive refrigerant from thereceiver, and the secondary inlet fluidly coupled to receive refrigerantfluid from the liquid-side outlet of the liquid separator.
 40. Thesystem of claim 39, wherein the ejector is configured to pump asecondary refrigerant fluid flow received at the secondary inlet fromthe liquid side outlet using energy of a primary refrigerant flow fromthe receiver outlet.
 41. The system of claim 31, further comprising apump having an inlet and an outlet, with the inlet fluidly coupled tothe liquid-side outlet of the liquid separator and the outlet fluidlycoupled to an inlet of the gated evaporator.
 42. The system of claim 41,wherein the pump is configured to circulate a refrigerant fluid flowreceived from the liquid-side outlet of the liquid separator to theinlet of the gated evaporator.
 43. The system of claim 41, furthercomprising a control system configured to control operation of the gatedevaporator, the control system comprising a processor device, memory andstorage operatively connected.
 44. The system of claim 43, wherein thecontrol system is configured to: produce a first control signal todirect transported refrigerant fluid to enter a first set of fewer thanthe like plurality of evaporator sections over a first interval, andinhibits the refrigerant fluid to enter a second, different set of thefewer than the like plurality of evaporator sections over the firstinterval; and produce a second control signal to direct the transportedrefrigerant fluid that enters the gated evaporator to contact a third,different set of the evaporator sections over a second, subsequentinterval, and inhibits the refrigerant fluid to enter a fourth,different set of the fewer than the plural evaporator sections over thesecond interval.
 45. A thermal management method, comprising:transporting a refrigerant fluid from a receiver, through a gatedevaporator having a plurality of evaporator sections configured toextract heat from a plurality of heat loads when the plurality of heatloads are in thermal conductive or convective contact or are inproximity to the gated evaporator, through a flow control device tocontrol to control refrigerant fluid pressure upstream of the flowcontrol device, and to an exhaust line of an open-circuit refrigerationsystem (OCRS); directing the transported refrigerant fluid to enter afirst set of “n”- “x” number of the plurality of evaporator sectionsover a first interval, while inhibiting the refrigerant fluid to enter asecond, different set of “x” number of the plurality of evaporatorsections over the first interval, where “n” is a total number of theplurality of evaporator sections; switching the refrigerant fluid todirect the transported refrigerant fluid that enters the gatedevaporator to contact a third, different set of “n”- “x”′ number of theplurality of evaporator sections over a second, subsequent interval,while inhibiting the refrigerant fluid to enter a fourth, different setof “x”′ number of the plurality of evaporator sections over the secondinterval; and discharging refrigerant vapor that is generated by theplurality of heat loads from the exhaust line so that the dischargedrefrigerant vapor is not returned to the receiver.
 46. The method ofclaim 45, wherein the flow control device is a first flow controldevice, and the method further comprises controlling a vapor quality ofthe refrigerant fluid at an outlet of the gated evaporator by operationof a second flow control device.
 47. The method of claim 45, whereinswitching occurs by controlling operation of a plurality of controlvalves coupled to a plurality of outlets of an inlet distributor of thegated evaporator, with the plurality of outlets being coupled to inletsof the plurality of evaporator sections.
 48. The method of claim 45,further comprising collecting refrigerant flows by an outlet collectorhaving a plurality of inlets coupled to evaporator section outlets. 49.The method of claim 45, further comprising: expanding, by the pluralityof control valves, the refrigerant fluid to generate a refrigerant fluidmixture comprising liquid refrigerant and refrigerant vapor; anddirecting the refrigerant fluid mixture into the correspondingevaporator sections.
 50. The method of claim 49, wherein the pluralityof control valves are expansion valves that are configured toselectively stop refrigerant fluid through the expansion valves.
 51. Themethod of claim 49, wherein the plurality of “n” number of controlvalves are expansion valves that are not configured to stop refrigerantfluid through the expansion valves, and the method further comprisesoperating a plurality of solenoid control valves fluidly coupled to theexpansion valves to selectively stop the refrigerant fluid through theexpansion valves.
 52. The method of claim 49, wherein the plurality ofcontrol valves are configured to selectively perform a constant-enthalpyexpansion of the liquid refrigerant fluid to generate the refrigerantfluid mixture for the evaporator sections.
 53. The method of claim 45,wherein the refrigerant fluid comprises ammonia.
 54. The method of claim45, wherein the plurality of control valves are configured to controltemperatures of the heat loads.
 55. The method of claim 45, whereindischarging comprises discharging the refrigerant vapor through aback-pressure regulator.
 56. The method of claim 45, wherein theback-pressure regulator is configured to receive refrigerant vaporgenerated in the gated evaporator and to regulate the pressure of therefrigerant fluid upstream from the back-pressure regulator.
 57. Themethod of claim 45, wherein the back-pressure regulator is configured todischarge the refrigerant vapor through the exhaust line withoutreturning the refrigerant vapor to the receiver.
 58. The method of claim45, wherein the refrigerant fluid from the exhaust line is discharged sothat the discharged refrigerant vapor is not returned to the receiver.59. The method of claim 45, further comprising operating a controlsystem to: respond to signals from sensors to control operation of theplurality of control valves; and process the signals from the sensor toswitch “x” number of the plurality of control valves to inhibitrefrigerant flow through the “x” number of the plurality of controlvalves during the first interval, with “x” having a value that is atleast one less than “n.”
 60. The method of claim 59, further comprisingoperating the control system to: process the signals as time periodsignals to indicate that “x” number of uncooled evaporator sections havereached a maximum time period for proper heat load operation, with “x”having a value that is at least one less than “n”.
 61. The method ofclaim 59, further comprising operating the control system to: processthe signals as temperature signals to indicate that “x” number of theuncooled evaporator sections have reached the maximum heat loadtemperature rise during the heat load operation, with “x” having a valuethat is at least one less than “n.”
 62. The method of claim 59, furthercomprising operating the control system to: process the signals astemperature signals to indicate that “x” number of uncooled evaporatorsections have reached a maximum evaporator section temperature riseduring the heat load operation, with “x” having a value that is at leastone less than “n.”
 63. The method of claim 45, wherein the flow controldevice is a first flow control device, and the method further includescontrolling vapor quality at the outlet of the gated evaporator with asecond flow control device fluidly coupled between the receiver outletand the inlet to the flow distributer.
 64. The method of claim 45,wherein transporting the refrigerant fluid comprises transporting therefrigerant fluid through a closed-circuit refrigeration system (CCRS)that is integrated with the OCRS.
 65. The method of claim 64, furthercomprising transporting the refrigerant fluid through a liquid separatorhaving an inlet, a vapor-side outlet, and a liquid-side outlet.
 66. Themethod of claim 65, further comprising: transporting the refrigerantfluid to a compressor of the CCRS, the compressor having a compressorinlet coupled to the vapor-side outlet and having a compressor outlet;and transporting the refrigerant fluid to a condenser having a condenserinlet coupled to the compressor outlet and having a condenser outletcoupled to an inlet of the receiver to condense a superheated vapor atthe condenser inlet by removing heat from the refrigerant fluid.
 67. Themethod of claim 66, further comprising receiving refrigerant fluid fromthe receiver by a recuperative heat exchanger that has a first fluidpath that receives the refrigerant fluid from the receiver and a secondfluid path that receives refrigerant vapor from the vapor-side outlet,with the second fluid path providing thermal contact between therefrigerant fluid leaving the receiver and refrigerant vapor passingthrough the recuperative heat exchanger.
 68. The method of claim 67,further comprising evaporating any remaining refrigerant liquid in therecuperative heat exchanger prior to the inlet of the compressor. 69.The method of claim 65, further comprising transporting refrigerantfluid from the liquid side outlet of the liquid separator to a secondaryinlet of an ejector that further has a primary inlet and an outlet, withthe primary inlet fluidly coupled to receive refrigerant from thereceiver, and the outlet fluidly coupled to deliver refrigerant fluid tothe inlet of the liquid separator.
 70. The method of claim 69, furthercomprising pumping, with the ejector, a secondary refrigerant fluid flowreceived by the secondary inlet from the liquid side outlet using energyof a primary refrigerant flow from the receiver outlet.
 71. The methodof claim 65, further comprising pumping, with a pump, refrigerant liquidfrom the liquid-side outlet of the liquid separator to an inlet of thegated evaporator.